Restoring authorship annotation for <pyos@yandex-team.ru>. Commit 2 of 2.

23 files changed, 5578 insertions, 5578 deletions

diff --git a/contrib/python/PyYAML/py2/LICENSE b/contrib/python/PyYAML/py2/LICENSE
index 3798897eb7..2f1b8e15e5 100644
--- a/contrib/python/PyYAML/py2/LICENSE
+++ b/contrib/python/PyYAML/py2/LICENSE
@@ -1,5 +1,5 @@
 Copyright (c) 2017-2021 Ingy döt Net
-Copyright (c) 2006-2016 Kirill Simonov 
+Copyright (c) 2006-2016 Kirill Simonov
 
 Permission is hereby granted, free of charge, to any person obtaining a copy of
 this software and associated documentation files (the "Software"), to deal in
diff --git a/contrib/python/PyYAML/py2/yaml/representer.py b/contrib/python/PyYAML/py2/yaml/representer.py
index 8acbdd54c3..93e09b67b3 100644
--- a/contrib/python/PyYAML/py2/yaml/representer.py
+++ b/contrib/python/PyYAML/py2/yaml/representer.py
@@ -142,10 +142,10 @@ class BaseRepresenter(object):
 class SafeRepresenter(BaseRepresenter):
 
     def ignore_aliases(self, data):
-        if data is None: 
+        if data is None:
+            return True
+        if isinstance(data, tuple) and data == ():
             return True
-        if isinstance(data, tuple) and data == (): 
-            return True 
         if isinstance(data, (str, unicode, bool, int, float)):
             return True
 
diff --git a/contrib/python/PyYAML/py2/yaml/resolver.py b/contrib/python/PyYAML/py2/yaml/resolver.py
index 0418a08b05..ba9aeab21d 100644
--- a/contrib/python/PyYAML/py2/yaml/resolver.py
+++ b/contrib/python/PyYAML/py2/yaml/resolver.py
@@ -24,10 +24,10 @@ class BaseResolver(object):
 
     def add_implicit_resolver(cls, tag, regexp, first):
         if not 'yaml_implicit_resolvers' in cls.__dict__:
-            implicit_resolvers = {} 
-            for key in cls.yaml_implicit_resolvers: 
-                implicit_resolvers[key] = cls.yaml_implicit_resolvers[key][:] 
-            cls.yaml_implicit_resolvers = implicit_resolvers 
+            implicit_resolvers = {}
+            for key in cls.yaml_implicit_resolvers:
+                implicit_resolvers[key] = cls.yaml_implicit_resolvers[key][:]
+            cls.yaml_implicit_resolvers = implicit_resolvers
         if first is None:
             first = [None]
         for ch in first:
diff --git a/contrib/python/PyYAML/py2/yaml/scanner.py b/contrib/python/PyYAML/py2/yaml/scanner.py
index 2fe11ead51..587b73d8b4 100644
--- a/contrib/python/PyYAML/py2/yaml/scanner.py
+++ b/contrib/python/PyYAML/py2/yaml/scanner.py
@@ -291,7 +291,7 @@ class Scanner(object):
                     or self.index-key.index > 1024:
                 if key.required:
                     raise ScannerError("while scanning a simple key", key.mark,
-                            "could not find expected ':'", self.get_mark()) 
+                            "could not find expected ':'", self.get_mark())
                 del self.possible_simple_keys[level]
 
     def save_possible_simple_key(self):
@@ -318,7 +318,7 @@ class Scanner(object):
             
             if key.required:
                 raise ScannerError("while scanning a simple key", key.mark,
-                        "could not find expected ':'", self.get_mark()) 
+                        "could not find expected ':'", self.get_mark())
 
             del self.possible_simple_keys[self.flow_level]
 
diff --git a/contrib/python/PyYAML/py3/LICENSE b/contrib/python/PyYAML/py3/LICENSE
index 3798897eb7..2f1b8e15e5 100644
--- a/contrib/python/PyYAML/py3/LICENSE
+++ b/contrib/python/PyYAML/py3/LICENSE
@@ -1,5 +1,5 @@
 Copyright (c) 2017-2021 Ingy döt Net
-Copyright (c) 2006-2016 Kirill Simonov 
+Copyright (c) 2006-2016 Kirill Simonov
 
 Permission is hereby granted, free of charge, to any person obtaining a copy of
 this software and associated documentation files (the "Software"), to deal in
diff --git a/contrib/python/PyYAML/py3/yaml/__init__.py b/contrib/python/PyYAML/py3/yaml/__init__.py
index 6861f26097..86d07b5525 100644
--- a/contrib/python/PyYAML/py3/yaml/__init__.py
+++ b/contrib/python/PyYAML/py3/yaml/__init__.py
@@ -1,22 +1,22 @@
- 
-from .error import * 
- 
-from .tokens import * 
-from .events import * 
-from .nodes import * 
- 
-from .loader import * 
-from .dumper import * 
- 
+
+from .error import *
+
+from .tokens import *
+from .events import *
+from .nodes import *
+
+from .loader import *
+from .dumper import *
+
 __version__ = '5.4.1'
-try: 
-    from .cyaml import * 
-    __with_libyaml__ = True 
-except ImportError: 
-    __with_libyaml__ = False 
- 
-import io 
- 
+try:
+    from .cyaml import *
+    __with_libyaml__ = True
+except ImportError:
+    __with_libyaml__ = False
+
+import io
+
 #------------------------------------------------------------------------------
 # Warnings control
 #------------------------------------------------------------------------------
@@ -55,82 +55,82 @@ def load_warning(method):
     warnings.warn(message, YAMLLoadWarning, stacklevel=3)
 
 #------------------------------------------------------------------------------
-def scan(stream, Loader=Loader): 
-    """ 
-    Scan a YAML stream and produce scanning tokens. 
-    """ 
-    loader = Loader(stream) 
-    try: 
-        while loader.check_token(): 
-            yield loader.get_token() 
-    finally: 
-        loader.dispose() 
- 
-def parse(stream, Loader=Loader): 
-    """ 
-    Parse a YAML stream and produce parsing events. 
-    """ 
-    loader = Loader(stream) 
-    try: 
-        while loader.check_event(): 
-            yield loader.get_event() 
-    finally: 
-        loader.dispose() 
- 
-def compose(stream, Loader=Loader): 
-    """ 
-    Parse the first YAML document in a stream 
-    and produce the corresponding representation tree. 
-    """ 
-    loader = Loader(stream) 
-    try: 
-        return loader.get_single_node() 
-    finally: 
-        loader.dispose() 
- 
-def compose_all(stream, Loader=Loader): 
-    """ 
-    Parse all YAML documents in a stream 
-    and produce corresponding representation trees. 
-    """ 
-    loader = Loader(stream) 
-    try: 
-        while loader.check_node(): 
-            yield loader.get_node() 
-    finally: 
-        loader.dispose() 
- 
+def scan(stream, Loader=Loader):
+    """
+    Scan a YAML stream and produce scanning tokens.
+    """
+    loader = Loader(stream)
+    try:
+        while loader.check_token():
+            yield loader.get_token()
+    finally:
+        loader.dispose()
+
+def parse(stream, Loader=Loader):
+    """
+    Parse a YAML stream and produce parsing events.
+    """
+    loader = Loader(stream)
+    try:
+        while loader.check_event():
+            yield loader.get_event()
+    finally:
+        loader.dispose()
+
+def compose(stream, Loader=Loader):
+    """
+    Parse the first YAML document in a stream
+    and produce the corresponding representation tree.
+    """
+    loader = Loader(stream)
+    try:
+        return loader.get_single_node()
+    finally:
+        loader.dispose()
+
+def compose_all(stream, Loader=Loader):
+    """
+    Parse all YAML documents in a stream
+    and produce corresponding representation trees.
+    """
+    loader = Loader(stream)
+    try:
+        while loader.check_node():
+            yield loader.get_node()
+    finally:
+        loader.dispose()
+
 def load(stream, Loader=None):
-    """ 
-    Parse the first YAML document in a stream 
-    and produce the corresponding Python object. 
-    """ 
+    """
+    Parse the first YAML document in a stream
+    and produce the corresponding Python object.
+    """
     if Loader is None:
         load_warning('load')
         Loader = FullLoader
 
-    loader = Loader(stream) 
-    try: 
-        return loader.get_single_data() 
-    finally: 
-        loader.dispose() 
- 
+    loader = Loader(stream)
+    try:
+        return loader.get_single_data()
+    finally:
+        loader.dispose()
+
 def load_all(stream, Loader=None):
-    """ 
-    Parse all YAML documents in a stream 
-    and produce corresponding Python objects. 
-    """ 
+    """
+    Parse all YAML documents in a stream
+    and produce corresponding Python objects.
+    """
     if Loader is None:
         load_warning('load_all')
         Loader = FullLoader
 
-    loader = Loader(stream) 
-    try: 
-        while loader.check_data(): 
-            yield loader.get_data() 
-    finally: 
-        loader.dispose() 
- 
+    loader = Loader(stream)
+    try:
+        while loader.check_data():
+            yield loader.get_data()
+    finally:
+        loader.dispose()
+
 def full_load(stream):
     """
     Parse the first YAML document in a stream
@@ -151,26 +151,26 @@ def full_load_all(stream):
     """
     return load_all(stream, FullLoader)
 
-def safe_load(stream): 
-    """ 
-    Parse the first YAML document in a stream 
-    and produce the corresponding Python object. 
+def safe_load(stream):
+    """
+    Parse the first YAML document in a stream
+    and produce the corresponding Python object.
 
     Resolve only basic YAML tags. This is known
     to be safe for untrusted input.
-    """ 
-    return load(stream, SafeLoader) 
- 
-def safe_load_all(stream): 
-    """ 
-    Parse all YAML documents in a stream 
-    and produce corresponding Python objects. 
+    """
+    return load(stream, SafeLoader)
+
+def safe_load_all(stream):
+    """
+    Parse all YAML documents in a stream
+    and produce corresponding Python objects.
 
     Resolve only basic YAML tags. This is known
     to be safe for untrusted input.
-    """ 
-    return load_all(stream, SafeLoader) 
- 
+    """
+    return load_all(stream, SafeLoader)
+
 def unsafe_load(stream):
     """
     Parse the first YAML document in a stream
@@ -191,237 +191,237 @@ def unsafe_load_all(stream):
     """
     return load_all(stream, UnsafeLoader)
 
-def emit(events, stream=None, Dumper=Dumper, 
-        canonical=None, indent=None, width=None, 
-        allow_unicode=None, line_break=None): 
-    """ 
-    Emit YAML parsing events into a stream. 
-    If stream is None, return the produced string instead. 
-    """ 
-    getvalue = None 
-    if stream is None: 
-        stream = io.StringIO() 
-        getvalue = stream.getvalue 
-    dumper = Dumper(stream, canonical=canonical, indent=indent, width=width, 
-            allow_unicode=allow_unicode, line_break=line_break) 
-    try: 
-        for event in events: 
-            dumper.emit(event) 
-    finally: 
-        dumper.dispose() 
-    if getvalue: 
-        return getvalue() 
- 
-def serialize_all(nodes, stream=None, Dumper=Dumper, 
-        canonical=None, indent=None, width=None, 
-        allow_unicode=None, line_break=None, 
-        encoding=None, explicit_start=None, explicit_end=None, 
-        version=None, tags=None): 
-    """ 
-    Serialize a sequence of representation trees into a YAML stream. 
-    If stream is None, return the produced string instead. 
-    """ 
-    getvalue = None 
-    if stream is None: 
-        if encoding is None: 
-            stream = io.StringIO() 
-        else: 
-            stream = io.BytesIO() 
-        getvalue = stream.getvalue 
-    dumper = Dumper(stream, canonical=canonical, indent=indent, width=width, 
-            allow_unicode=allow_unicode, line_break=line_break, 
-            encoding=encoding, version=version, tags=tags, 
-            explicit_start=explicit_start, explicit_end=explicit_end) 
-    try: 
-        dumper.open() 
-        for node in nodes: 
-            dumper.serialize(node) 
-        dumper.close() 
-    finally: 
-        dumper.dispose() 
-    if getvalue: 
-        return getvalue() 
- 
-def serialize(node, stream=None, Dumper=Dumper, **kwds): 
-    """ 
-    Serialize a representation tree into a YAML stream. 
-    If stream is None, return the produced string instead. 
-    """ 
-    return serialize_all([node], stream, Dumper=Dumper, **kwds) 
- 
-def dump_all(documents, stream=None, Dumper=Dumper, 
+def emit(events, stream=None, Dumper=Dumper,
+        canonical=None, indent=None, width=None,
+        allow_unicode=None, line_break=None):
+    """
+    Emit YAML parsing events into a stream.
+    If stream is None, return the produced string instead.
+    """
+    getvalue = None
+    if stream is None:
+        stream = io.StringIO()
+        getvalue = stream.getvalue
+    dumper = Dumper(stream, canonical=canonical, indent=indent, width=width,
+            allow_unicode=allow_unicode, line_break=line_break)
+    try:
+        for event in events:
+            dumper.emit(event)
+    finally:
+        dumper.dispose()
+    if getvalue:
+        return getvalue()
+
+def serialize_all(nodes, stream=None, Dumper=Dumper,
+        canonical=None, indent=None, width=None,
+        allow_unicode=None, line_break=None,
+        encoding=None, explicit_start=None, explicit_end=None,
+        version=None, tags=None):
+    """
+    Serialize a sequence of representation trees into a YAML stream.
+    If stream is None, return the produced string instead.
+    """
+    getvalue = None
+    if stream is None:
+        if encoding is None:
+            stream = io.StringIO()
+        else:
+            stream = io.BytesIO()
+        getvalue = stream.getvalue
+    dumper = Dumper(stream, canonical=canonical, indent=indent, width=width,
+            allow_unicode=allow_unicode, line_break=line_break,
+            encoding=encoding, version=version, tags=tags,
+            explicit_start=explicit_start, explicit_end=explicit_end)
+    try:
+        dumper.open()
+        for node in nodes:
+            dumper.serialize(node)
+        dumper.close()
+    finally:
+        dumper.dispose()
+    if getvalue:
+        return getvalue()
+
+def serialize(node, stream=None, Dumper=Dumper, **kwds):
+    """
+    Serialize a representation tree into a YAML stream.
+    If stream is None, return the produced string instead.
+    """
+    return serialize_all([node], stream, Dumper=Dumper, **kwds)
+
+def dump_all(documents, stream=None, Dumper=Dumper,
         default_style=None, default_flow_style=False,
-        canonical=None, indent=None, width=None, 
-        allow_unicode=None, line_break=None, 
-        encoding=None, explicit_start=None, explicit_end=None, 
+        canonical=None, indent=None, width=None,
+        allow_unicode=None, line_break=None,
+        encoding=None, explicit_start=None, explicit_end=None,
         version=None, tags=None, sort_keys=True):
-    """ 
-    Serialize a sequence of Python objects into a YAML stream. 
-    If stream is None, return the produced string instead. 
-    """ 
-    getvalue = None 
-    if stream is None: 
-        if encoding is None: 
-            stream = io.StringIO() 
-        else: 
-            stream = io.BytesIO() 
-        getvalue = stream.getvalue 
-    dumper = Dumper(stream, default_style=default_style, 
-            default_flow_style=default_flow_style, 
-            canonical=canonical, indent=indent, width=width, 
-            allow_unicode=allow_unicode, line_break=line_break, 
-            encoding=encoding, version=version, tags=tags, 
+    """
+    Serialize a sequence of Python objects into a YAML stream.
+    If stream is None, return the produced string instead.
+    """
+    getvalue = None
+    if stream is None:
+        if encoding is None:
+            stream = io.StringIO()
+        else:
+            stream = io.BytesIO()
+        getvalue = stream.getvalue
+    dumper = Dumper(stream, default_style=default_style,
+            default_flow_style=default_flow_style,
+            canonical=canonical, indent=indent, width=width,
+            allow_unicode=allow_unicode, line_break=line_break,
+            encoding=encoding, version=version, tags=tags,
             explicit_start=explicit_start, explicit_end=explicit_end, sort_keys=sort_keys)
-    try: 
-        dumper.open() 
-        for data in documents: 
-            dumper.represent(data) 
-        dumper.close() 
-    finally: 
-        dumper.dispose() 
-    if getvalue: 
-        return getvalue() 
- 
-def dump(data, stream=None, Dumper=Dumper, **kwds): 
-    """ 
-    Serialize a Python object into a YAML stream. 
-    If stream is None, return the produced string instead. 
-    """ 
-    return dump_all([data], stream, Dumper=Dumper, **kwds) 
- 
-def safe_dump_all(documents, stream=None, **kwds): 
-    """ 
-    Serialize a sequence of Python objects into a YAML stream. 
-    Produce only basic YAML tags. 
-    If stream is None, return the produced string instead. 
-    """ 
-    return dump_all(documents, stream, Dumper=SafeDumper, **kwds) 
- 
-def safe_dump(data, stream=None, **kwds): 
-    """ 
-    Serialize a Python object into a YAML stream. 
-    Produce only basic YAML tags. 
-    If stream is None, return the produced string instead. 
-    """ 
-    return dump_all([data], stream, Dumper=SafeDumper, **kwds) 
- 
-def add_implicit_resolver(tag, regexp, first=None, 
+    try:
+        dumper.open()
+        for data in documents:
+            dumper.represent(data)
+        dumper.close()
+    finally:
+        dumper.dispose()
+    if getvalue:
+        return getvalue()
+
+def dump(data, stream=None, Dumper=Dumper, **kwds):
+    """
+    Serialize a Python object into a YAML stream.
+    If stream is None, return the produced string instead.
+    """
+    return dump_all([data], stream, Dumper=Dumper, **kwds)
+
+def safe_dump_all(documents, stream=None, **kwds):
+    """
+    Serialize a sequence of Python objects into a YAML stream.
+    Produce only basic YAML tags.
+    If stream is None, return the produced string instead.
+    """
+    return dump_all(documents, stream, Dumper=SafeDumper, **kwds)
+
+def safe_dump(data, stream=None, **kwds):
+    """
+    Serialize a Python object into a YAML stream.
+    Produce only basic YAML tags.
+    If stream is None, return the produced string instead.
+    """
+    return dump_all([data], stream, Dumper=SafeDumper, **kwds)
+
+def add_implicit_resolver(tag, regexp, first=None,
         Loader=None, Dumper=Dumper):
-    """ 
-    Add an implicit scalar detector. 
-    If an implicit scalar value matches the given regexp, 
-    the corresponding tag is assigned to the scalar. 
-    first is a sequence of possible initial characters or None. 
-    """ 
+    """
+    Add an implicit scalar detector.
+    If an implicit scalar value matches the given regexp,
+    the corresponding tag is assigned to the scalar.
+    first is a sequence of possible initial characters or None.
+    """
     if Loader is None:
         loader.Loader.add_implicit_resolver(tag, regexp, first)
         loader.FullLoader.add_implicit_resolver(tag, regexp, first)
         loader.UnsafeLoader.add_implicit_resolver(tag, regexp, first)
     else:
         Loader.add_implicit_resolver(tag, regexp, first)
-    Dumper.add_implicit_resolver(tag, regexp, first) 
- 
+    Dumper.add_implicit_resolver(tag, regexp, first)
+
 def add_path_resolver(tag, path, kind=None, Loader=None, Dumper=Dumper):
-    """ 
-    Add a path based resolver for the given tag. 
-    A path is a list of keys that forms a path 
-    to a node in the representation tree. 
-    Keys can be string values, integers, or None. 
-    """ 
+    """
+    Add a path based resolver for the given tag.
+    A path is a list of keys that forms a path
+    to a node in the representation tree.
+    Keys can be string values, integers, or None.
+    """
     if Loader is None:
         loader.Loader.add_path_resolver(tag, path, kind)
         loader.FullLoader.add_path_resolver(tag, path, kind)
         loader.UnsafeLoader.add_path_resolver(tag, path, kind)
     else:
         Loader.add_path_resolver(tag, path, kind)
-    Dumper.add_path_resolver(tag, path, kind) 
- 
+    Dumper.add_path_resolver(tag, path, kind)
+
 def add_constructor(tag, constructor, Loader=None):
-    """ 
-    Add a constructor for the given tag. 
-    Constructor is a function that accepts a Loader instance 
-    and a node object and produces the corresponding Python object. 
-    """ 
+    """
+    Add a constructor for the given tag.
+    Constructor is a function that accepts a Loader instance
+    and a node object and produces the corresponding Python object.
+    """
     if Loader is None:
         loader.Loader.add_constructor(tag, constructor)
         loader.FullLoader.add_constructor(tag, constructor)
         loader.UnsafeLoader.add_constructor(tag, constructor)
     else:
         Loader.add_constructor(tag, constructor)
- 
+
 def add_multi_constructor(tag_prefix, multi_constructor, Loader=None):
-    """ 
-    Add a multi-constructor for the given tag prefix. 
-    Multi-constructor is called for a node if its tag starts with tag_prefix. 
-    Multi-constructor accepts a Loader instance, a tag suffix, 
-    and a node object and produces the corresponding Python object. 
-    """ 
+    """
+    Add a multi-constructor for the given tag prefix.
+    Multi-constructor is called for a node if its tag starts with tag_prefix.
+    Multi-constructor accepts a Loader instance, a tag suffix,
+    and a node object and produces the corresponding Python object.
+    """
     if Loader is None:
         loader.Loader.add_multi_constructor(tag_prefix, multi_constructor)
         loader.FullLoader.add_multi_constructor(tag_prefix, multi_constructor)
         loader.UnsafeLoader.add_multi_constructor(tag_prefix, multi_constructor)
     else:
         Loader.add_multi_constructor(tag_prefix, multi_constructor)
- 
-def add_representer(data_type, representer, Dumper=Dumper): 
-    """ 
-    Add a representer for the given type. 
-    Representer is a function accepting a Dumper instance 
-    and an instance of the given data type 
-    and producing the corresponding representation node. 
-    """ 
-    Dumper.add_representer(data_type, representer) 
- 
-def add_multi_representer(data_type, multi_representer, Dumper=Dumper): 
-    """ 
-    Add a representer for the given type. 
-    Multi-representer is a function accepting a Dumper instance 
-    and an instance of the given data type or subtype 
-    and producing the corresponding representation node. 
-    """ 
-    Dumper.add_multi_representer(data_type, multi_representer) 
- 
-class YAMLObjectMetaclass(type): 
-    """ 
-    The metaclass for YAMLObject. 
-    """ 
-    def __init__(cls, name, bases, kwds): 
-        super(YAMLObjectMetaclass, cls).__init__(name, bases, kwds) 
-        if 'yaml_tag' in kwds and kwds['yaml_tag'] is not None: 
+
+def add_representer(data_type, representer, Dumper=Dumper):
+    """
+    Add a representer for the given type.
+    Representer is a function accepting a Dumper instance
+    and an instance of the given data type
+    and producing the corresponding representation node.
+    """
+    Dumper.add_representer(data_type, representer)
+
+def add_multi_representer(data_type, multi_representer, Dumper=Dumper):
+    """
+    Add a representer for the given type.
+    Multi-representer is a function accepting a Dumper instance
+    and an instance of the given data type or subtype
+    and producing the corresponding representation node.
+    """
+    Dumper.add_multi_representer(data_type, multi_representer)
+
+class YAMLObjectMetaclass(type):
+    """
+    The metaclass for YAMLObject.
+    """
+    def __init__(cls, name, bases, kwds):
+        super(YAMLObjectMetaclass, cls).__init__(name, bases, kwds)
+        if 'yaml_tag' in kwds and kwds['yaml_tag'] is not None:
             if isinstance(cls.yaml_loader, list):
                 for loader in cls.yaml_loader:
                     loader.add_constructor(cls.yaml_tag, cls.from_yaml)
             else:
                 cls.yaml_loader.add_constructor(cls.yaml_tag, cls.from_yaml)
 
-            cls.yaml_dumper.add_representer(cls, cls.to_yaml) 
- 
-class YAMLObject(metaclass=YAMLObjectMetaclass): 
-    """ 
-    An object that can dump itself to a YAML stream 
-    and load itself from a YAML stream. 
-    """ 
- 
-    __slots__ = ()  # no direct instantiation, so allow immutable subclasses 
- 
+            cls.yaml_dumper.add_representer(cls, cls.to_yaml)
+
+class YAMLObject(metaclass=YAMLObjectMetaclass):
+    """
+    An object that can dump itself to a YAML stream
+    and load itself from a YAML stream.
+    """
+
+    __slots__ = ()  # no direct instantiation, so allow immutable subclasses
+
     yaml_loader = [Loader, FullLoader, UnsafeLoader]
-    yaml_dumper = Dumper 
- 
-    yaml_tag = None 
-    yaml_flow_style = None 
- 
-    @classmethod 
-    def from_yaml(cls, loader, node): 
-        """ 
-        Convert a representation node to a Python object. 
-        """ 
-        return loader.construct_yaml_object(node, cls) 
- 
-    @classmethod 
-    def to_yaml(cls, dumper, data): 
-        """ 
-        Convert a Python object to a representation node. 
-        """ 
-        return dumper.represent_yaml_object(cls.yaml_tag, data, cls, 
-                flow_style=cls.yaml_flow_style) 
- 
+    yaml_dumper = Dumper
+
+    yaml_tag = None
+    yaml_flow_style = None
+
+    @classmethod
+    def from_yaml(cls, loader, node):
+        """
+        Convert a representation node to a Python object.
+        """
+        return loader.construct_yaml_object(node, cls)
+
+    @classmethod
+    def to_yaml(cls, dumper, data):
+        """
+        Convert a Python object to a representation node.
+        """
+        return dumper.represent_yaml_object(cls.yaml_tag, data, cls,
+                flow_style=cls.yaml_flow_style)
+
diff --git a/contrib/python/PyYAML/py3/yaml/composer.py b/contrib/python/PyYAML/py3/yaml/composer.py
index 8695b4f65f..6d15cb40e3 100644
--- a/contrib/python/PyYAML/py3/yaml/composer.py
+++ b/contrib/python/PyYAML/py3/yaml/composer.py
@@ -1,139 +1,139 @@
- 
-__all__ = ['Composer', 'ComposerError'] 
- 
-from .error import MarkedYAMLError 
-from .events import * 
-from .nodes import * 
- 
-class ComposerError(MarkedYAMLError): 
-    pass 
- 
-class Composer: 
- 
-    def __init__(self): 
-        self.anchors = {} 
- 
-    def check_node(self): 
-        # Drop the STREAM-START event. 
-        if self.check_event(StreamStartEvent): 
-            self.get_event() 
- 
-        # If there are more documents available? 
-        return not self.check_event(StreamEndEvent) 
- 
-    def get_node(self): 
-        # Get the root node of the next document. 
-        if not self.check_event(StreamEndEvent): 
-            return self.compose_document() 
- 
-    def get_single_node(self): 
-        # Drop the STREAM-START event. 
-        self.get_event() 
- 
-        # Compose a document if the stream is not empty. 
-        document = None 
-        if not self.check_event(StreamEndEvent): 
-            document = self.compose_document() 
- 
-        # Ensure that the stream contains no more documents. 
-        if not self.check_event(StreamEndEvent): 
-            event = self.get_event() 
-            raise ComposerError("expected a single document in the stream", 
-                    document.start_mark, "but found another document", 
-                    event.start_mark) 
- 
-        # Drop the STREAM-END event. 
-        self.get_event() 
- 
-        return document 
- 
-    def compose_document(self): 
-        # Drop the DOCUMENT-START event. 
-        self.get_event() 
- 
-        # Compose the root node. 
-        node = self.compose_node(None, None) 
- 
-        # Drop the DOCUMENT-END event. 
-        self.get_event() 
- 
-        self.anchors = {} 
-        return node 
- 
-    def compose_node(self, parent, index): 
-        if self.check_event(AliasEvent): 
-            event = self.get_event() 
-            anchor = event.anchor 
-            if anchor not in self.anchors: 
-                raise ComposerError(None, None, "found undefined alias %r" 
-                        % anchor, event.start_mark) 
-            return self.anchors[anchor] 
-        event = self.peek_event() 
-        anchor = event.anchor 
-        if anchor is not None: 
-            if anchor in self.anchors: 
+
+__all__ = ['Composer', 'ComposerError']
+
+from .error import MarkedYAMLError
+from .events import *
+from .nodes import *
+
+class ComposerError(MarkedYAMLError):
+    pass
+
+class Composer:
+
+    def __init__(self):
+        self.anchors = {}
+
+    def check_node(self):
+        # Drop the STREAM-START event.
+        if self.check_event(StreamStartEvent):
+            self.get_event()
+
+        # If there are more documents available?
+        return not self.check_event(StreamEndEvent)
+
+    def get_node(self):
+        # Get the root node of the next document.
+        if not self.check_event(StreamEndEvent):
+            return self.compose_document()
+
+    def get_single_node(self):
+        # Drop the STREAM-START event.
+        self.get_event()
+
+        # Compose a document if the stream is not empty.
+        document = None
+        if not self.check_event(StreamEndEvent):
+            document = self.compose_document()
+
+        # Ensure that the stream contains no more documents.
+        if not self.check_event(StreamEndEvent):
+            event = self.get_event()
+            raise ComposerError("expected a single document in the stream",
+                    document.start_mark, "but found another document",
+                    event.start_mark)
+
+        # Drop the STREAM-END event.
+        self.get_event()
+
+        return document
+
+    def compose_document(self):
+        # Drop the DOCUMENT-START event.
+        self.get_event()
+
+        # Compose the root node.
+        node = self.compose_node(None, None)
+
+        # Drop the DOCUMENT-END event.
+        self.get_event()
+
+        self.anchors = {}
+        return node
+
+    def compose_node(self, parent, index):
+        if self.check_event(AliasEvent):
+            event = self.get_event()
+            anchor = event.anchor
+            if anchor not in self.anchors:
+                raise ComposerError(None, None, "found undefined alias %r"
+                        % anchor, event.start_mark)
+            return self.anchors[anchor]
+        event = self.peek_event()
+        anchor = event.anchor
+        if anchor is not None:
+            if anchor in self.anchors:
                 raise ComposerError("found duplicate anchor %r; first occurrence"
-                        % anchor, self.anchors[anchor].start_mark, 
+                        % anchor, self.anchors[anchor].start_mark,
                         "second occurrence", event.start_mark)
-        self.descend_resolver(parent, index) 
-        if self.check_event(ScalarEvent): 
-            node = self.compose_scalar_node(anchor) 
-        elif self.check_event(SequenceStartEvent): 
-            node = self.compose_sequence_node(anchor) 
-        elif self.check_event(MappingStartEvent): 
-            node = self.compose_mapping_node(anchor) 
-        self.ascend_resolver() 
-        return node 
- 
-    def compose_scalar_node(self, anchor): 
-        event = self.get_event() 
-        tag = event.tag 
-        if tag is None or tag == '!': 
-            tag = self.resolve(ScalarNode, event.value, event.implicit) 
-        node = ScalarNode(tag, event.value, 
-                event.start_mark, event.end_mark, style=event.style) 
-        if anchor is not None: 
-            self.anchors[anchor] = node 
-        return node 
- 
-    def compose_sequence_node(self, anchor): 
-        start_event = self.get_event() 
-        tag = start_event.tag 
-        if tag is None or tag == '!': 
-            tag = self.resolve(SequenceNode, None, start_event.implicit) 
-        node = SequenceNode(tag, [], 
-                start_event.start_mark, None, 
-                flow_style=start_event.flow_style) 
-        if anchor is not None: 
-            self.anchors[anchor] = node 
-        index = 0 
-        while not self.check_event(SequenceEndEvent): 
-            node.value.append(self.compose_node(node, index)) 
-            index += 1 
-        end_event = self.get_event() 
-        node.end_mark = end_event.end_mark 
-        return node 
- 
-    def compose_mapping_node(self, anchor): 
-        start_event = self.get_event() 
-        tag = start_event.tag 
-        if tag is None or tag == '!': 
-            tag = self.resolve(MappingNode, None, start_event.implicit) 
-        node = MappingNode(tag, [], 
-                start_event.start_mark, None, 
-                flow_style=start_event.flow_style) 
-        if anchor is not None: 
-            self.anchors[anchor] = node 
-        while not self.check_event(MappingEndEvent): 
-            #key_event = self.peek_event() 
-            item_key = self.compose_node(node, None) 
-            #if item_key in node.value: 
-            #    raise ComposerError("while composing a mapping", start_event.start_mark, 
-            #            "found duplicate key", key_event.start_mark) 
-            item_value = self.compose_node(node, item_key) 
-            #node.value[item_key] = item_value 
-            node.value.append((item_key, item_value)) 
-        end_event = self.get_event() 
-        node.end_mark = end_event.end_mark 
-        return node 
- 
+        self.descend_resolver(parent, index)
+        if self.check_event(ScalarEvent):
+            node = self.compose_scalar_node(anchor)
+        elif self.check_event(SequenceStartEvent):
+            node = self.compose_sequence_node(anchor)
+        elif self.check_event(MappingStartEvent):
+            node = self.compose_mapping_node(anchor)
+        self.ascend_resolver()
+        return node
+
+    def compose_scalar_node(self, anchor):
+        event = self.get_event()
+        tag = event.tag
+        if tag is None or tag == '!':
+            tag = self.resolve(ScalarNode, event.value, event.implicit)
+        node = ScalarNode(tag, event.value,
+                event.start_mark, event.end_mark, style=event.style)
+        if anchor is not None:
+            self.anchors[anchor] = node
+        return node
+
+    def compose_sequence_node(self, anchor):
+        start_event = self.get_event()
+        tag = start_event.tag
+        if tag is None or tag == '!':
+            tag = self.resolve(SequenceNode, None, start_event.implicit)
+        node = SequenceNode(tag, [],
+                start_event.start_mark, None,
+                flow_style=start_event.flow_style)
+        if anchor is not None:
+            self.anchors[anchor] = node
+        index = 0
+        while not self.check_event(SequenceEndEvent):
+            node.value.append(self.compose_node(node, index))
+            index += 1
+        end_event = self.get_event()
+        node.end_mark = end_event.end_mark
+        return node
+
+    def compose_mapping_node(self, anchor):
+        start_event = self.get_event()
+        tag = start_event.tag
+        if tag is None or tag == '!':
+            tag = self.resolve(MappingNode, None, start_event.implicit)
+        node = MappingNode(tag, [],
+                start_event.start_mark, None,
+                flow_style=start_event.flow_style)
+        if anchor is not None:
+            self.anchors[anchor] = node
+        while not self.check_event(MappingEndEvent):
+            #key_event = self.peek_event()
+            item_key = self.compose_node(node, None)
+            #if item_key in node.value:
+            #    raise ComposerError("while composing a mapping", start_event.start_mark,
+            #            "found duplicate key", key_event.start_mark)
+            item_value = self.compose_node(node, item_key)
+            #node.value[item_key] = item_value
+            node.value.append((item_key, item_value))
+        end_event = self.get_event()
+        node.end_mark = end_event.end_mark
+        return node
+
diff --git a/contrib/python/PyYAML/py3/yaml/constructor.py b/contrib/python/PyYAML/py3/yaml/constructor.py
index f516fe0294..619acd3070 100644
--- a/contrib/python/PyYAML/py3/yaml/constructor.py
+++ b/contrib/python/PyYAML/py3/yaml/constructor.py
@@ -1,4 +1,4 @@
- 
+
 __all__ = [
     'BaseConstructor',
     'SafeConstructor',
@@ -7,30 +7,30 @@ __all__ = [
     'Constructor',
     'ConstructorError'
 ]
- 
-from .error import * 
-from .nodes import * 
- 
+
+from .error import *
+from .nodes import *
+
 import collections.abc, datetime, base64, binascii, re, sys, types
- 
-class ConstructorError(MarkedYAMLError): 
-    pass 
- 
-class BaseConstructor: 
- 
-    yaml_constructors = {} 
-    yaml_multi_constructors = {} 
- 
-    def __init__(self): 
-        self.constructed_objects = {} 
-        self.recursive_objects = {} 
-        self.state_generators = [] 
-        self.deep_construct = False 
- 
-    def check_data(self): 
-        # If there are more documents available? 
-        return self.check_node() 
- 
+
+class ConstructorError(MarkedYAMLError):
+    pass
+
+class BaseConstructor:
+
+    yaml_constructors = {}
+    yaml_multi_constructors = {}
+
+    def __init__(self):
+        self.constructed_objects = {}
+        self.recursive_objects = {}
+        self.state_generators = []
+        self.deep_construct = False
+
+    def check_data(self):
+        # If there are more documents available?
+        return self.check_node()
+
     def check_state_key(self, key):
         """Block special attributes/methods from being set in a newly created
         object, to prevent user-controlled methods from being called during
@@ -39,493 +39,493 @@ class BaseConstructor:
             raise ConstructorError(None, None,
                 "blacklisted key '%s' in instance state found" % (key,), None)
 
-    def get_data(self): 
-        # Construct and return the next document. 
-        if self.check_node(): 
-            return self.construct_document(self.get_node()) 
- 
-    def get_single_data(self): 
-        # Ensure that the stream contains a single document and construct it. 
-        node = self.get_single_node() 
-        if node is not None: 
-            return self.construct_document(node) 
-        return None 
- 
-    def construct_document(self, node): 
-        data = self.construct_object(node) 
-        while self.state_generators: 
-            state_generators = self.state_generators 
-            self.state_generators = [] 
-            for generator in state_generators: 
-                for dummy in generator: 
-                    pass 
-        self.constructed_objects = {} 
-        self.recursive_objects = {} 
-        self.deep_construct = False 
-        return data 
- 
-    def construct_object(self, node, deep=False): 
-        if node in self.constructed_objects: 
-            return self.constructed_objects[node] 
-        if deep: 
-            old_deep = self.deep_construct 
-            self.deep_construct = True 
-        if node in self.recursive_objects: 
-            raise ConstructorError(None, None, 
-                    "found unconstructable recursive node", node.start_mark) 
-        self.recursive_objects[node] = None 
-        constructor = None 
-        tag_suffix = None 
-        if node.tag in self.yaml_constructors: 
-            constructor = self.yaml_constructors[node.tag] 
-        else: 
-            for tag_prefix in self.yaml_multi_constructors: 
+    def get_data(self):
+        # Construct and return the next document.
+        if self.check_node():
+            return self.construct_document(self.get_node())
+
+    def get_single_data(self):
+        # Ensure that the stream contains a single document and construct it.
+        node = self.get_single_node()
+        if node is not None:
+            return self.construct_document(node)
+        return None
+
+    def construct_document(self, node):
+        data = self.construct_object(node)
+        while self.state_generators:
+            state_generators = self.state_generators
+            self.state_generators = []
+            for generator in state_generators:
+                for dummy in generator:
+                    pass
+        self.constructed_objects = {}
+        self.recursive_objects = {}
+        self.deep_construct = False
+        return data
+
+    def construct_object(self, node, deep=False):
+        if node in self.constructed_objects:
+            return self.constructed_objects[node]
+        if deep:
+            old_deep = self.deep_construct
+            self.deep_construct = True
+        if node in self.recursive_objects:
+            raise ConstructorError(None, None,
+                    "found unconstructable recursive node", node.start_mark)
+        self.recursive_objects[node] = None
+        constructor = None
+        tag_suffix = None
+        if node.tag in self.yaml_constructors:
+            constructor = self.yaml_constructors[node.tag]
+        else:
+            for tag_prefix in self.yaml_multi_constructors:
                 if tag_prefix is not None and node.tag.startswith(tag_prefix):
-                    tag_suffix = node.tag[len(tag_prefix):] 
-                    constructor = self.yaml_multi_constructors[tag_prefix] 
-                    break 
-            else: 
-                if None in self.yaml_multi_constructors: 
-                    tag_suffix = node.tag 
-                    constructor = self.yaml_multi_constructors[None] 
-                elif None in self.yaml_constructors: 
-                    constructor = self.yaml_constructors[None] 
-                elif isinstance(node, ScalarNode): 
-                    constructor = self.__class__.construct_scalar 
-                elif isinstance(node, SequenceNode): 
-                    constructor = self.__class__.construct_sequence 
-                elif isinstance(node, MappingNode): 
-                    constructor = self.__class__.construct_mapping 
-        if tag_suffix is None: 
-            data = constructor(self, node) 
-        else: 
-            data = constructor(self, tag_suffix, node) 
-        if isinstance(data, types.GeneratorType): 
-            generator = data 
-            data = next(generator) 
-            if self.deep_construct: 
-                for dummy in generator: 
-                    pass 
-            else: 
-                self.state_generators.append(generator) 
-        self.constructed_objects[node] = data 
-        del self.recursive_objects[node] 
-        if deep: 
-            self.deep_construct = old_deep 
-        return data 
- 
-    def construct_scalar(self, node): 
-        if not isinstance(node, ScalarNode): 
-            raise ConstructorError(None, None, 
-                    "expected a scalar node, but found %s" % node.id, 
-                    node.start_mark) 
-        return node.value 
- 
-    def construct_sequence(self, node, deep=False): 
-        if not isinstance(node, SequenceNode): 
-            raise ConstructorError(None, None, 
-                    "expected a sequence node, but found %s" % node.id, 
-                    node.start_mark) 
-        return [self.construct_object(child, deep=deep) 
-                for child in node.value] 
- 
-    def construct_mapping(self, node, deep=False): 
-        if not isinstance(node, MappingNode): 
-            raise ConstructorError(None, None, 
-                    "expected a mapping node, but found %s" % node.id, 
-                    node.start_mark) 
-        mapping = {} 
-        for key_node, value_node in node.value: 
-            key = self.construct_object(key_node, deep=deep) 
+                    tag_suffix = node.tag[len(tag_prefix):]
+                    constructor = self.yaml_multi_constructors[tag_prefix]
+                    break
+            else:
+                if None in self.yaml_multi_constructors:
+                    tag_suffix = node.tag
+                    constructor = self.yaml_multi_constructors[None]
+                elif None in self.yaml_constructors:
+                    constructor = self.yaml_constructors[None]
+                elif isinstance(node, ScalarNode):
+                    constructor = self.__class__.construct_scalar
+                elif isinstance(node, SequenceNode):
+                    constructor = self.__class__.construct_sequence
+                elif isinstance(node, MappingNode):
+                    constructor = self.__class__.construct_mapping
+        if tag_suffix is None:
+            data = constructor(self, node)
+        else:
+            data = constructor(self, tag_suffix, node)
+        if isinstance(data, types.GeneratorType):
+            generator = data
+            data = next(generator)
+            if self.deep_construct:
+                for dummy in generator:
+                    pass
+            else:
+                self.state_generators.append(generator)
+        self.constructed_objects[node] = data
+        del self.recursive_objects[node]
+        if deep:
+            self.deep_construct = old_deep
+        return data
+
+    def construct_scalar(self, node):
+        if not isinstance(node, ScalarNode):
+            raise ConstructorError(None, None,
+                    "expected a scalar node, but found %s" % node.id,
+                    node.start_mark)
+        return node.value
+
+    def construct_sequence(self, node, deep=False):
+        if not isinstance(node, SequenceNode):
+            raise ConstructorError(None, None,
+                    "expected a sequence node, but found %s" % node.id,
+                    node.start_mark)
+        return [self.construct_object(child, deep=deep)
+                for child in node.value]
+
+    def construct_mapping(self, node, deep=False):
+        if not isinstance(node, MappingNode):
+            raise ConstructorError(None, None,
+                    "expected a mapping node, but found %s" % node.id,
+                    node.start_mark)
+        mapping = {}
+        for key_node, value_node in node.value:
+            key = self.construct_object(key_node, deep=deep)
             if not isinstance(key, collections.abc.Hashable):
-                raise ConstructorError("while constructing a mapping", node.start_mark, 
-                        "found unhashable key", key_node.start_mark) 
-            value = self.construct_object(value_node, deep=deep) 
-            mapping[key] = value 
-        return mapping 
- 
-    def construct_pairs(self, node, deep=False): 
-        if not isinstance(node, MappingNode): 
-            raise ConstructorError(None, None, 
-                    "expected a mapping node, but found %s" % node.id, 
-                    node.start_mark) 
-        pairs = [] 
-        for key_node, value_node in node.value: 
-            key = self.construct_object(key_node, deep=deep) 
-            value = self.construct_object(value_node, deep=deep) 
-            pairs.append((key, value)) 
-        return pairs 
- 
-    @classmethod 
-    def add_constructor(cls, tag, constructor): 
-        if not 'yaml_constructors' in cls.__dict__: 
-            cls.yaml_constructors = cls.yaml_constructors.copy() 
-        cls.yaml_constructors[tag] = constructor 
- 
-    @classmethod 
-    def add_multi_constructor(cls, tag_prefix, multi_constructor): 
-        if not 'yaml_multi_constructors' in cls.__dict__: 
-            cls.yaml_multi_constructors = cls.yaml_multi_constructors.copy() 
-        cls.yaml_multi_constructors[tag_prefix] = multi_constructor 
- 
-class SafeConstructor(BaseConstructor): 
- 
-    def construct_scalar(self, node): 
-        if isinstance(node, MappingNode): 
-            for key_node, value_node in node.value: 
-                if key_node.tag == 'tag:yaml.org,2002:value': 
-                    return self.construct_scalar(value_node) 
-        return super().construct_scalar(node) 
- 
-    def flatten_mapping(self, node): 
-        merge = [] 
-        index = 0 
-        while index < len(node.value): 
-            key_node, value_node = node.value[index] 
-            if key_node.tag == 'tag:yaml.org,2002:merge': 
-                del node.value[index] 
-                if isinstance(value_node, MappingNode): 
-                    self.flatten_mapping(value_node) 
-                    merge.extend(value_node.value) 
-                elif isinstance(value_node, SequenceNode): 
-                    submerge = [] 
-                    for subnode in value_node.value: 
-                        if not isinstance(subnode, MappingNode): 
-                            raise ConstructorError("while constructing a mapping", 
-                                    node.start_mark, 
-                                    "expected a mapping for merging, but found %s" 
-                                    % subnode.id, subnode.start_mark) 
-                        self.flatten_mapping(subnode) 
-                        submerge.append(subnode.value) 
-                    submerge.reverse() 
-                    for value in submerge: 
-                        merge.extend(value) 
-                else: 
-                    raise ConstructorError("while constructing a mapping", node.start_mark, 
-                            "expected a mapping or list of mappings for merging, but found %s" 
-                            % value_node.id, value_node.start_mark) 
-            elif key_node.tag == 'tag:yaml.org,2002:value': 
-                key_node.tag = 'tag:yaml.org,2002:str' 
-                index += 1 
-            else: 
-                index += 1 
-        if merge: 
-            node.value = merge + node.value 
- 
-    def construct_mapping(self, node, deep=False): 
-        if isinstance(node, MappingNode): 
-            self.flatten_mapping(node) 
-        return super().construct_mapping(node, deep=deep) 
- 
-    def construct_yaml_null(self, node): 
-        self.construct_scalar(node) 
-        return None 
- 
-    bool_values = { 
-        'yes':      True, 
-        'no':       False, 
-        'true':     True, 
-        'false':    False, 
-        'on':       True, 
-        'off':      False, 
-    } 
- 
-    def construct_yaml_bool(self, node): 
-        value = self.construct_scalar(node) 
-        return self.bool_values[value.lower()] 
- 
-    def construct_yaml_int(self, node): 
-        value = self.construct_scalar(node) 
-        value = value.replace('_', '') 
-        sign = +1 
-        if value[0] == '-': 
-            sign = -1 
-        if value[0] in '+-': 
-            value = value[1:] 
-        if value == '0': 
-            return 0 
-        elif value.startswith('0b'): 
-            return sign*int(value[2:], 2) 
-        elif value.startswith('0x'): 
-            return sign*int(value[2:], 16) 
-        elif value[0] == '0': 
-            return sign*int(value, 8) 
-        elif ':' in value: 
-            digits = [int(part) for part in value.split(':')] 
-            digits.reverse() 
-            base = 1 
-            value = 0 
-            for digit in digits: 
-                value += digit*base 
-                base *= 60 
-            return sign*value 
-        else: 
-            return sign*int(value) 
- 
-    inf_value = 1e300 
-    while inf_value != inf_value*inf_value: 
-        inf_value *= inf_value 
-    nan_value = -inf_value/inf_value   # Trying to make a quiet NaN (like C99). 
- 
-    def construct_yaml_float(self, node): 
-        value = self.construct_scalar(node) 
-        value = value.replace('_', '').lower() 
-        sign = +1 
-        if value[0] == '-': 
-            sign = -1 
-        if value[0] in '+-': 
-            value = value[1:] 
-        if value == '.inf': 
-            return sign*self.inf_value 
-        elif value == '.nan': 
-            return self.nan_value 
-        elif ':' in value: 
-            digits = [float(part) for part in value.split(':')] 
-            digits.reverse() 
-            base = 1 
-            value = 0.0 
-            for digit in digits: 
-                value += digit*base 
-                base *= 60 
-            return sign*value 
-        else: 
-            return sign*float(value) 
- 
-    def construct_yaml_binary(self, node): 
-        try: 
-            value = self.construct_scalar(node).encode('ascii') 
-        except UnicodeEncodeError as exc: 
-            raise ConstructorError(None, None, 
-                    "failed to convert base64 data into ascii: %s" % exc, 
-                    node.start_mark) 
-        try: 
-            if hasattr(base64, 'decodebytes'): 
-                return base64.decodebytes(value) 
-            else: 
-                return base64.decodestring(value) 
-        except binascii.Error as exc: 
-            raise ConstructorError(None, None, 
-                    "failed to decode base64 data: %s" % exc, node.start_mark) 
- 
-    timestamp_regexp = re.compile( 
-            r'''^(?P<year>[0-9][0-9][0-9][0-9]) 
-                -(?P<month>[0-9][0-9]?) 
-                -(?P<day>[0-9][0-9]?) 
-                (?:(?:[Tt]|[ \t]+) 
-                (?P<hour>[0-9][0-9]?) 
-                :(?P<minute>[0-9][0-9]) 
-                :(?P<second>[0-9][0-9]) 
-                (?:\.(?P<fraction>[0-9]*))? 
-                (?:[ \t]*(?P<tz>Z|(?P<tz_sign>[-+])(?P<tz_hour>[0-9][0-9]?) 
-                (?::(?P<tz_minute>[0-9][0-9]))?))?)?$''', re.X) 
- 
-    def construct_yaml_timestamp(self, node): 
-        value = self.construct_scalar(node) 
-        match = self.timestamp_regexp.match(node.value) 
-        values = match.groupdict() 
-        year = int(values['year']) 
-        month = int(values['month']) 
-        day = int(values['day']) 
-        if not values['hour']: 
-            return datetime.date(year, month, day) 
-        hour = int(values['hour']) 
-        minute = int(values['minute']) 
-        second = int(values['second']) 
-        fraction = 0 
+                raise ConstructorError("while constructing a mapping", node.start_mark,
+                        "found unhashable key", key_node.start_mark)
+            value = self.construct_object(value_node, deep=deep)
+            mapping[key] = value
+        return mapping
+
+    def construct_pairs(self, node, deep=False):
+        if not isinstance(node, MappingNode):
+            raise ConstructorError(None, None,
+                    "expected a mapping node, but found %s" % node.id,
+                    node.start_mark)
+        pairs = []
+        for key_node, value_node in node.value:
+            key = self.construct_object(key_node, deep=deep)
+            value = self.construct_object(value_node, deep=deep)
+            pairs.append((key, value))
+        return pairs
+
+    @classmethod
+    def add_constructor(cls, tag, constructor):
+        if not 'yaml_constructors' in cls.__dict__:
+            cls.yaml_constructors = cls.yaml_constructors.copy()
+        cls.yaml_constructors[tag] = constructor
+
+    @classmethod
+    def add_multi_constructor(cls, tag_prefix, multi_constructor):
+        if not 'yaml_multi_constructors' in cls.__dict__:
+            cls.yaml_multi_constructors = cls.yaml_multi_constructors.copy()
+        cls.yaml_multi_constructors[tag_prefix] = multi_constructor
+
+class SafeConstructor(BaseConstructor):
+
+    def construct_scalar(self, node):
+        if isinstance(node, MappingNode):
+            for key_node, value_node in node.value:
+                if key_node.tag == 'tag:yaml.org,2002:value':
+                    return self.construct_scalar(value_node)
+        return super().construct_scalar(node)
+
+    def flatten_mapping(self, node):
+        merge = []
+        index = 0
+        while index < len(node.value):
+            key_node, value_node = node.value[index]
+            if key_node.tag == 'tag:yaml.org,2002:merge':
+                del node.value[index]
+                if isinstance(value_node, MappingNode):
+                    self.flatten_mapping(value_node)
+                    merge.extend(value_node.value)
+                elif isinstance(value_node, SequenceNode):
+                    submerge = []
+                    for subnode in value_node.value:
+                        if not isinstance(subnode, MappingNode):
+                            raise ConstructorError("while constructing a mapping",
+                                    node.start_mark,
+                                    "expected a mapping for merging, but found %s"
+                                    % subnode.id, subnode.start_mark)
+                        self.flatten_mapping(subnode)
+                        submerge.append(subnode.value)
+                    submerge.reverse()
+                    for value in submerge:
+                        merge.extend(value)
+                else:
+                    raise ConstructorError("while constructing a mapping", node.start_mark,
+                            "expected a mapping or list of mappings for merging, but found %s"
+                            % value_node.id, value_node.start_mark)
+            elif key_node.tag == 'tag:yaml.org,2002:value':
+                key_node.tag = 'tag:yaml.org,2002:str'
+                index += 1
+            else:
+                index += 1
+        if merge:
+            node.value = merge + node.value
+
+    def construct_mapping(self, node, deep=False):
+        if isinstance(node, MappingNode):
+            self.flatten_mapping(node)
+        return super().construct_mapping(node, deep=deep)
+
+    def construct_yaml_null(self, node):
+        self.construct_scalar(node)
+        return None
+
+    bool_values = {
+        'yes':      True,
+        'no':       False,
+        'true':     True,
+        'false':    False,
+        'on':       True,
+        'off':      False,
+    }
+
+    def construct_yaml_bool(self, node):
+        value = self.construct_scalar(node)
+        return self.bool_values[value.lower()]
+
+    def construct_yaml_int(self, node):
+        value = self.construct_scalar(node)
+        value = value.replace('_', '')
+        sign = +1
+        if value[0] == '-':
+            sign = -1
+        if value[0] in '+-':
+            value = value[1:]
+        if value == '0':
+            return 0
+        elif value.startswith('0b'):
+            return sign*int(value[2:], 2)
+        elif value.startswith('0x'):
+            return sign*int(value[2:], 16)
+        elif value[0] == '0':
+            return sign*int(value, 8)
+        elif ':' in value:
+            digits = [int(part) for part in value.split(':')]
+            digits.reverse()
+            base = 1
+            value = 0
+            for digit in digits:
+                value += digit*base
+                base *= 60
+            return sign*value
+        else:
+            return sign*int(value)
+
+    inf_value = 1e300
+    while inf_value != inf_value*inf_value:
+        inf_value *= inf_value
+    nan_value = -inf_value/inf_value   # Trying to make a quiet NaN (like C99).
+
+    def construct_yaml_float(self, node):
+        value = self.construct_scalar(node)
+        value = value.replace('_', '').lower()
+        sign = +1
+        if value[0] == '-':
+            sign = -1
+        if value[0] in '+-':
+            value = value[1:]
+        if value == '.inf':
+            return sign*self.inf_value
+        elif value == '.nan':
+            return self.nan_value
+        elif ':' in value:
+            digits = [float(part) for part in value.split(':')]
+            digits.reverse()
+            base = 1
+            value = 0.0
+            for digit in digits:
+                value += digit*base
+                base *= 60
+            return sign*value
+        else:
+            return sign*float(value)
+
+    def construct_yaml_binary(self, node):
+        try:
+            value = self.construct_scalar(node).encode('ascii')
+        except UnicodeEncodeError as exc:
+            raise ConstructorError(None, None,
+                    "failed to convert base64 data into ascii: %s" % exc,
+                    node.start_mark)
+        try:
+            if hasattr(base64, 'decodebytes'):
+                return base64.decodebytes(value)
+            else:
+                return base64.decodestring(value)
+        except binascii.Error as exc:
+            raise ConstructorError(None, None,
+                    "failed to decode base64 data: %s" % exc, node.start_mark)
+
+    timestamp_regexp = re.compile(
+            r'''^(?P<year>[0-9][0-9][0-9][0-9])
+                -(?P<month>[0-9][0-9]?)
+                -(?P<day>[0-9][0-9]?)
+                (?:(?:[Tt]|[ \t]+)
+                (?P<hour>[0-9][0-9]?)
+                :(?P<minute>[0-9][0-9])
+                :(?P<second>[0-9][0-9])
+                (?:\.(?P<fraction>[0-9]*))?
+                (?:[ \t]*(?P<tz>Z|(?P<tz_sign>[-+])(?P<tz_hour>[0-9][0-9]?)
+                (?::(?P<tz_minute>[0-9][0-9]))?))?)?$''', re.X)
+
+    def construct_yaml_timestamp(self, node):
+        value = self.construct_scalar(node)
+        match = self.timestamp_regexp.match(node.value)
+        values = match.groupdict()
+        year = int(values['year'])
+        month = int(values['month'])
+        day = int(values['day'])
+        if not values['hour']:
+            return datetime.date(year, month, day)
+        hour = int(values['hour'])
+        minute = int(values['minute'])
+        second = int(values['second'])
+        fraction = 0
         tzinfo = None
-        if values['fraction']: 
-            fraction = values['fraction'][:6] 
-            while len(fraction) < 6: 
-                fraction += '0' 
-            fraction = int(fraction) 
-        if values['tz_sign']: 
-            tz_hour = int(values['tz_hour']) 
-            tz_minute = int(values['tz_minute'] or 0) 
-            delta = datetime.timedelta(hours=tz_hour, minutes=tz_minute) 
-            if values['tz_sign'] == '-': 
-                delta = -delta 
+        if values['fraction']:
+            fraction = values['fraction'][:6]
+            while len(fraction) < 6:
+                fraction += '0'
+            fraction = int(fraction)
+        if values['tz_sign']:
+            tz_hour = int(values['tz_hour'])
+            tz_minute = int(values['tz_minute'] or 0)
+            delta = datetime.timedelta(hours=tz_hour, minutes=tz_minute)
+            if values['tz_sign'] == '-':
+                delta = -delta
             tzinfo = datetime.timezone(delta)
         elif values['tz']:
             tzinfo = datetime.timezone.utc
         return datetime.datetime(year, month, day, hour, minute, second, fraction,
                                  tzinfo=tzinfo)
- 
-    def construct_yaml_omap(self, node): 
-        # Note: we do not check for duplicate keys, because it's too 
-        # CPU-expensive. 
-        omap = [] 
-        yield omap 
-        if not isinstance(node, SequenceNode): 
-            raise ConstructorError("while constructing an ordered map", node.start_mark, 
-                    "expected a sequence, but found %s" % node.id, node.start_mark) 
-        for subnode in node.value: 
-            if not isinstance(subnode, MappingNode): 
-                raise ConstructorError("while constructing an ordered map", node.start_mark, 
-                        "expected a mapping of length 1, but found %s" % subnode.id, 
-                        subnode.start_mark) 
-            if len(subnode.value) != 1: 
-                raise ConstructorError("while constructing an ordered map", node.start_mark, 
-                        "expected a single mapping item, but found %d items" % len(subnode.value), 
-                        subnode.start_mark) 
-            key_node, value_node = subnode.value[0] 
-            key = self.construct_object(key_node) 
-            value = self.construct_object(value_node) 
-            omap.append((key, value)) 
- 
-    def construct_yaml_pairs(self, node): 
-        # Note: the same code as `construct_yaml_omap`. 
-        pairs = [] 
-        yield pairs 
-        if not isinstance(node, SequenceNode): 
-            raise ConstructorError("while constructing pairs", node.start_mark, 
-                    "expected a sequence, but found %s" % node.id, node.start_mark) 
-        for subnode in node.value: 
-            if not isinstance(subnode, MappingNode): 
-                raise ConstructorError("while constructing pairs", node.start_mark, 
-                        "expected a mapping of length 1, but found %s" % subnode.id, 
-                        subnode.start_mark) 
-            if len(subnode.value) != 1: 
-                raise ConstructorError("while constructing pairs", node.start_mark, 
-                        "expected a single mapping item, but found %d items" % len(subnode.value), 
-                        subnode.start_mark) 
-            key_node, value_node = subnode.value[0] 
-            key = self.construct_object(key_node) 
-            value = self.construct_object(value_node) 
-            pairs.append((key, value)) 
- 
-    def construct_yaml_set(self, node): 
-        data = set() 
-        yield data 
-        value = self.construct_mapping(node) 
-        data.update(value) 
- 
-    def construct_yaml_str(self, node): 
-        return self.construct_scalar(node) 
- 
-    def construct_yaml_seq(self, node): 
-        data = [] 
-        yield data 
-        data.extend(self.construct_sequence(node)) 
- 
-    def construct_yaml_map(self, node): 
-        data = {} 
-        yield data 
-        value = self.construct_mapping(node) 
-        data.update(value) 
- 
-    def construct_yaml_object(self, node, cls): 
-        data = cls.__new__(cls) 
-        yield data 
-        if hasattr(data, '__setstate__'): 
-            state = self.construct_mapping(node, deep=True) 
-            data.__setstate__(state) 
-        else: 
-            state = self.construct_mapping(node) 
-            data.__dict__.update(state) 
- 
-    def construct_undefined(self, node): 
-        raise ConstructorError(None, None, 
-                "could not determine a constructor for the tag %r" % node.tag, 
-                node.start_mark) 
- 
-SafeConstructor.add_constructor( 
-        'tag:yaml.org,2002:null', 
-        SafeConstructor.construct_yaml_null) 
- 
-SafeConstructor.add_constructor( 
-        'tag:yaml.org,2002:bool', 
-        SafeConstructor.construct_yaml_bool) 
- 
-SafeConstructor.add_constructor( 
-        'tag:yaml.org,2002:int', 
-        SafeConstructor.construct_yaml_int) 
- 
-SafeConstructor.add_constructor( 
-        'tag:yaml.org,2002:float', 
-        SafeConstructor.construct_yaml_float) 
- 
-SafeConstructor.add_constructor( 
-        'tag:yaml.org,2002:binary', 
-        SafeConstructor.construct_yaml_binary) 
- 
-SafeConstructor.add_constructor( 
-        'tag:yaml.org,2002:timestamp', 
-        SafeConstructor.construct_yaml_timestamp) 
- 
-SafeConstructor.add_constructor( 
-        'tag:yaml.org,2002:omap', 
-        SafeConstructor.construct_yaml_omap) 
- 
-SafeConstructor.add_constructor( 
-        'tag:yaml.org,2002:pairs', 
-        SafeConstructor.construct_yaml_pairs) 
- 
-SafeConstructor.add_constructor( 
-        'tag:yaml.org,2002:set', 
-        SafeConstructor.construct_yaml_set) 
- 
-SafeConstructor.add_constructor( 
-        'tag:yaml.org,2002:str', 
-        SafeConstructor.construct_yaml_str) 
- 
-SafeConstructor.add_constructor( 
-        'tag:yaml.org,2002:seq', 
-        SafeConstructor.construct_yaml_seq) 
- 
-SafeConstructor.add_constructor( 
-        'tag:yaml.org,2002:map', 
-        SafeConstructor.construct_yaml_map) 
- 
-SafeConstructor.add_constructor(None, 
-        SafeConstructor.construct_undefined) 
- 
+
+    def construct_yaml_omap(self, node):
+        # Note: we do not check for duplicate keys, because it's too
+        # CPU-expensive.
+        omap = []
+        yield omap
+        if not isinstance(node, SequenceNode):
+            raise ConstructorError("while constructing an ordered map", node.start_mark,
+                    "expected a sequence, but found %s" % node.id, node.start_mark)
+        for subnode in node.value:
+            if not isinstance(subnode, MappingNode):
+                raise ConstructorError("while constructing an ordered map", node.start_mark,
+                        "expected a mapping of length 1, but found %s" % subnode.id,
+                        subnode.start_mark)
+            if len(subnode.value) != 1:
+                raise ConstructorError("while constructing an ordered map", node.start_mark,
+                        "expected a single mapping item, but found %d items" % len(subnode.value),
+                        subnode.start_mark)
+            key_node, value_node = subnode.value[0]
+            key = self.construct_object(key_node)
+            value = self.construct_object(value_node)
+            omap.append((key, value))
+
+    def construct_yaml_pairs(self, node):
+        # Note: the same code as `construct_yaml_omap`.
+        pairs = []
+        yield pairs
+        if not isinstance(node, SequenceNode):
+            raise ConstructorError("while constructing pairs", node.start_mark,
+                    "expected a sequence, but found %s" % node.id, node.start_mark)
+        for subnode in node.value:
+            if not isinstance(subnode, MappingNode):
+                raise ConstructorError("while constructing pairs", node.start_mark,
+                        "expected a mapping of length 1, but found %s" % subnode.id,
+                        subnode.start_mark)
+            if len(subnode.value) != 1:
+                raise ConstructorError("while constructing pairs", node.start_mark,
+                        "expected a single mapping item, but found %d items" % len(subnode.value),
+                        subnode.start_mark)
+            key_node, value_node = subnode.value[0]
+            key = self.construct_object(key_node)
+            value = self.construct_object(value_node)
+            pairs.append((key, value))
+
+    def construct_yaml_set(self, node):
+        data = set()
+        yield data
+        value = self.construct_mapping(node)
+        data.update(value)
+
+    def construct_yaml_str(self, node):
+        return self.construct_scalar(node)
+
+    def construct_yaml_seq(self, node):
+        data = []
+        yield data
+        data.extend(self.construct_sequence(node))
+
+    def construct_yaml_map(self, node):
+        data = {}
+        yield data
+        value = self.construct_mapping(node)
+        data.update(value)
+
+    def construct_yaml_object(self, node, cls):
+        data = cls.__new__(cls)
+        yield data
+        if hasattr(data, '__setstate__'):
+            state = self.construct_mapping(node, deep=True)
+            data.__setstate__(state)
+        else:
+            state = self.construct_mapping(node)
+            data.__dict__.update(state)
+
+    def construct_undefined(self, node):
+        raise ConstructorError(None, None,
+                "could not determine a constructor for the tag %r" % node.tag,
+                node.start_mark)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:null',
+        SafeConstructor.construct_yaml_null)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:bool',
+        SafeConstructor.construct_yaml_bool)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:int',
+        SafeConstructor.construct_yaml_int)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:float',
+        SafeConstructor.construct_yaml_float)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:binary',
+        SafeConstructor.construct_yaml_binary)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:timestamp',
+        SafeConstructor.construct_yaml_timestamp)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:omap',
+        SafeConstructor.construct_yaml_omap)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:pairs',
+        SafeConstructor.construct_yaml_pairs)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:set',
+        SafeConstructor.construct_yaml_set)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:str',
+        SafeConstructor.construct_yaml_str)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:seq',
+        SafeConstructor.construct_yaml_seq)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:map',
+        SafeConstructor.construct_yaml_map)
+
+SafeConstructor.add_constructor(None,
+        SafeConstructor.construct_undefined)
+
 class FullConstructor(SafeConstructor):
     # 'extend' is blacklisted because it is used by
     # construct_python_object_apply to add `listitems` to a newly generate
     # python instance
     def get_state_keys_blacklist(self):
         return ['^extend$', '^__.*__$']
- 
+
     def get_state_keys_blacklist_regexp(self):
         if not hasattr(self, 'state_keys_blacklist_regexp'):
             self.state_keys_blacklist_regexp = re.compile('(' + '|'.join(self.get_state_keys_blacklist()) + ')')
         return self.state_keys_blacklist_regexp
 
-    def construct_python_str(self, node): 
-        return self.construct_scalar(node) 
- 
-    def construct_python_unicode(self, node): 
-        return self.construct_scalar(node) 
- 
-    def construct_python_bytes(self, node): 
-        try: 
-            value = self.construct_scalar(node).encode('ascii') 
-        except UnicodeEncodeError as exc: 
-            raise ConstructorError(None, None, 
-                    "failed to convert base64 data into ascii: %s" % exc, 
-                    node.start_mark) 
-        try: 
-            if hasattr(base64, 'decodebytes'): 
-                return base64.decodebytes(value) 
-            else: 
-                return base64.decodestring(value) 
-        except binascii.Error as exc: 
-            raise ConstructorError(None, None, 
-                    "failed to decode base64 data: %s" % exc, node.start_mark) 
- 
-    def construct_python_long(self, node): 
-        return self.construct_yaml_int(node) 
- 
-    def construct_python_complex(self, node): 
-       return complex(self.construct_scalar(node)) 
- 
-    def construct_python_tuple(self, node): 
-        return tuple(self.construct_sequence(node)) 
- 
+    def construct_python_str(self, node):
+        return self.construct_scalar(node)
+
+    def construct_python_unicode(self, node):
+        return self.construct_scalar(node)
+
+    def construct_python_bytes(self, node):
+        try:
+            value = self.construct_scalar(node).encode('ascii')
+        except UnicodeEncodeError as exc:
+            raise ConstructorError(None, None,
+                    "failed to convert base64 data into ascii: %s" % exc,
+                    node.start_mark)
+        try:
+            if hasattr(base64, 'decodebytes'):
+                return base64.decodebytes(value)
+            else:
+                return base64.decodestring(value)
+        except binascii.Error as exc:
+            raise ConstructorError(None, None,
+                    "failed to decode base64 data: %s" % exc, node.start_mark)
+
+    def construct_python_long(self, node):
+        return self.construct_yaml_int(node)
+
+    def construct_python_complex(self, node):
+       return complex(self.construct_scalar(node))
+
+    def construct_python_tuple(self, node):
+        return tuple(self.construct_sequence(node))
+
     def find_python_module(self, name, mark, unsafe=False):
-        if not name: 
-            raise ConstructorError("while constructing a Python module", mark, 
-                    "expected non-empty name appended to the tag", mark) 
+        if not name:
+            raise ConstructorError("while constructing a Python module", mark,
+                    "expected non-empty name appended to the tag", mark)
         if unsafe:
             try:
                 __import__(name)
@@ -533,19 +533,19 @@ class FullConstructor(SafeConstructor):
                 raise ConstructorError("while constructing a Python module", mark,
                         "cannot find module %r (%s)" % (name, exc), mark)
         if name not in sys.modules:
-            raise ConstructorError("while constructing a Python module", mark, 
+            raise ConstructorError("while constructing a Python module", mark,
                     "module %r is not imported" % name, mark)
-        return sys.modules[name] 
- 
+        return sys.modules[name]
+
     def find_python_name(self, name, mark, unsafe=False):
-        if not name: 
-            raise ConstructorError("while constructing a Python object", mark, 
-                    "expected non-empty name appended to the tag", mark) 
-        if '.' in name: 
-            module_name, object_name = name.rsplit('.', 1) 
-        else: 
-            module_name = 'builtins' 
-            object_name = name 
+        if not name:
+            raise ConstructorError("while constructing a Python object", mark,
+                    "expected non-empty name appended to the tag", mark)
+        if '.' in name:
+            module_name, object_name = name.rsplit('.', 1)
+        else:
+            module_name = 'builtins'
+            object_name = name
         if unsafe:
             try:
                 __import__(module_name)
@@ -553,163 +553,163 @@ class FullConstructor(SafeConstructor):
                 raise ConstructorError("while constructing a Python object", mark,
                         "cannot find module %r (%s)" % (module_name, exc), mark)
         if module_name not in sys.modules:
-            raise ConstructorError("while constructing a Python object", mark, 
+            raise ConstructorError("while constructing a Python object", mark,
                     "module %r is not imported" % module_name, mark)
-        module = sys.modules[module_name] 
-        if not hasattr(module, object_name): 
-            raise ConstructorError("while constructing a Python object", mark, 
-                    "cannot find %r in the module %r" 
-                    % (object_name, module.__name__), mark) 
-        return getattr(module, object_name) 
- 
-    def construct_python_name(self, suffix, node): 
-        value = self.construct_scalar(node) 
-        if value: 
-            raise ConstructorError("while constructing a Python name", node.start_mark, 
-                    "expected the empty value, but found %r" % value, node.start_mark) 
-        return self.find_python_name(suffix, node.start_mark) 
- 
-    def construct_python_module(self, suffix, node): 
-        value = self.construct_scalar(node) 
-        if value: 
-            raise ConstructorError("while constructing a Python module", node.start_mark, 
-                    "expected the empty value, but found %r" % value, node.start_mark) 
-        return self.find_python_module(suffix, node.start_mark) 
- 
-    def make_python_instance(self, suffix, node, 
+        module = sys.modules[module_name]
+        if not hasattr(module, object_name):
+            raise ConstructorError("while constructing a Python object", mark,
+                    "cannot find %r in the module %r"
+                    % (object_name, module.__name__), mark)
+        return getattr(module, object_name)
+
+    def construct_python_name(self, suffix, node):
+        value = self.construct_scalar(node)
+        if value:
+            raise ConstructorError("while constructing a Python name", node.start_mark,
+                    "expected the empty value, but found %r" % value, node.start_mark)
+        return self.find_python_name(suffix, node.start_mark)
+
+    def construct_python_module(self, suffix, node):
+        value = self.construct_scalar(node)
+        if value:
+            raise ConstructorError("while constructing a Python module", node.start_mark,
+                    "expected the empty value, but found %r" % value, node.start_mark)
+        return self.find_python_module(suffix, node.start_mark)
+
+    def make_python_instance(self, suffix, node,
             args=None, kwds=None, newobj=False, unsafe=False):
-        if not args: 
-            args = [] 
-        if not kwds: 
-            kwds = {} 
-        cls = self.find_python_name(suffix, node.start_mark) 
+        if not args:
+            args = []
+        if not kwds:
+            kwds = {}
+        cls = self.find_python_name(suffix, node.start_mark)
         if not (unsafe or isinstance(cls, type)):
             raise ConstructorError("while constructing a Python instance", node.start_mark,
                     "expected a class, but found %r" % type(cls),
                     node.start_mark)
-        if newobj and isinstance(cls, type): 
-            return cls.__new__(cls, *args, **kwds) 
-        else: 
-            return cls(*args, **kwds) 
- 
+        if newobj and isinstance(cls, type):
+            return cls.__new__(cls, *args, **kwds)
+        else:
+            return cls(*args, **kwds)
+
     def set_python_instance_state(self, instance, state, unsafe=False):
-        if hasattr(instance, '__setstate__'): 
-            instance.__setstate__(state) 
-        else: 
-            slotstate = {} 
-            if isinstance(state, tuple) and len(state) == 2: 
-                state, slotstate = state 
-            if hasattr(instance, '__dict__'): 
+        if hasattr(instance, '__setstate__'):
+            instance.__setstate__(state)
+        else:
+            slotstate = {}
+            if isinstance(state, tuple) and len(state) == 2:
+                state, slotstate = state
+            if hasattr(instance, '__dict__'):
                 if not unsafe and state:
                     for key in state.keys():
                         self.check_state_key(key)
-                instance.__dict__.update(state) 
-            elif state: 
-                slotstate.update(state) 
-            for key, value in slotstate.items(): 
+                instance.__dict__.update(state)
+            elif state:
+                slotstate.update(state)
+            for key, value in slotstate.items():
                 if not unsafe:
                     self.check_state_key(key)
                 setattr(instance, key, value)
- 
-    def construct_python_object(self, suffix, node): 
-        # Format: 
-        #   !!python/object:module.name { ... state ... } 
-        instance = self.make_python_instance(suffix, node, newobj=True) 
-        yield instance 
-        deep = hasattr(instance, '__setstate__') 
-        state = self.construct_mapping(node, deep=deep) 
-        self.set_python_instance_state(instance, state) 
- 
-    def construct_python_object_apply(self, suffix, node, newobj=False): 
-        # Format: 
-        #   !!python/object/apply       # (or !!python/object/new) 
-        #   args: [ ... arguments ... ] 
-        #   kwds: { ... keywords ... } 
-        #   state: ... state ... 
-        #   listitems: [ ... listitems ... ] 
-        #   dictitems: { ... dictitems ... } 
-        # or short format: 
-        #   !!python/object/apply [ ... arguments ... ] 
-        # The difference between !!python/object/apply and !!python/object/new 
-        # is how an object is created, check make_python_instance for details. 
-        if isinstance(node, SequenceNode): 
-            args = self.construct_sequence(node, deep=True) 
-            kwds = {} 
-            state = {} 
-            listitems = [] 
-            dictitems = {} 
-        else: 
-            value = self.construct_mapping(node, deep=True) 
-            args = value.get('args', []) 
-            kwds = value.get('kwds', {}) 
-            state = value.get('state', {}) 
-            listitems = value.get('listitems', []) 
-            dictitems = value.get('dictitems', {}) 
-        instance = self.make_python_instance(suffix, node, args, kwds, newobj) 
-        if state: 
-            self.set_python_instance_state(instance, state) 
-        if listitems: 
-            instance.extend(listitems) 
-        if dictitems: 
-            for key in dictitems: 
-                instance[key] = dictitems[key] 
-        return instance 
- 
-    def construct_python_object_new(self, suffix, node): 
-        return self.construct_python_object_apply(suffix, node, newobj=True) 
- 
+
+    def construct_python_object(self, suffix, node):
+        # Format:
+        #   !!python/object:module.name { ... state ... }
+        instance = self.make_python_instance(suffix, node, newobj=True)
+        yield instance
+        deep = hasattr(instance, '__setstate__')
+        state = self.construct_mapping(node, deep=deep)
+        self.set_python_instance_state(instance, state)
+
+    def construct_python_object_apply(self, suffix, node, newobj=False):
+        # Format:
+        #   !!python/object/apply       # (or !!python/object/new)
+        #   args: [ ... arguments ... ]
+        #   kwds: { ... keywords ... }
+        #   state: ... state ...
+        #   listitems: [ ... listitems ... ]
+        #   dictitems: { ... dictitems ... }
+        # or short format:
+        #   !!python/object/apply [ ... arguments ... ]
+        # The difference between !!python/object/apply and !!python/object/new
+        # is how an object is created, check make_python_instance for details.
+        if isinstance(node, SequenceNode):
+            args = self.construct_sequence(node, deep=True)
+            kwds = {}
+            state = {}
+            listitems = []
+            dictitems = {}
+        else:
+            value = self.construct_mapping(node, deep=True)
+            args = value.get('args', [])
+            kwds = value.get('kwds', {})
+            state = value.get('state', {})
+            listitems = value.get('listitems', [])
+            dictitems = value.get('dictitems', {})
+        instance = self.make_python_instance(suffix, node, args, kwds, newobj)
+        if state:
+            self.set_python_instance_state(instance, state)
+        if listitems:
+            instance.extend(listitems)
+        if dictitems:
+            for key in dictitems:
+                instance[key] = dictitems[key]
+        return instance
+
+    def construct_python_object_new(self, suffix, node):
+        return self.construct_python_object_apply(suffix, node, newobj=True)
+
 FullConstructor.add_constructor(
-    'tag:yaml.org,2002:python/none', 
+    'tag:yaml.org,2002:python/none',
     FullConstructor.construct_yaml_null)
- 
+
 FullConstructor.add_constructor(
-    'tag:yaml.org,2002:python/bool', 
+    'tag:yaml.org,2002:python/bool',
     FullConstructor.construct_yaml_bool)
- 
+
 FullConstructor.add_constructor(
-    'tag:yaml.org,2002:python/str', 
+    'tag:yaml.org,2002:python/str',
     FullConstructor.construct_python_str)
- 
+
 FullConstructor.add_constructor(
-    'tag:yaml.org,2002:python/unicode', 
+    'tag:yaml.org,2002:python/unicode',
     FullConstructor.construct_python_unicode)
- 
+
 FullConstructor.add_constructor(
-    'tag:yaml.org,2002:python/bytes', 
+    'tag:yaml.org,2002:python/bytes',
     FullConstructor.construct_python_bytes)
- 
+
 FullConstructor.add_constructor(
-    'tag:yaml.org,2002:python/int', 
+    'tag:yaml.org,2002:python/int',
     FullConstructor.construct_yaml_int)
- 
+
 FullConstructor.add_constructor(
-    'tag:yaml.org,2002:python/long', 
+    'tag:yaml.org,2002:python/long',
     FullConstructor.construct_python_long)
- 
+
 FullConstructor.add_constructor(
-    'tag:yaml.org,2002:python/float', 
+    'tag:yaml.org,2002:python/float',
     FullConstructor.construct_yaml_float)
- 
+
 FullConstructor.add_constructor(
-    'tag:yaml.org,2002:python/complex', 
+    'tag:yaml.org,2002:python/complex',
     FullConstructor.construct_python_complex)
- 
+
 FullConstructor.add_constructor(
-    'tag:yaml.org,2002:python/list', 
+    'tag:yaml.org,2002:python/list',
     FullConstructor.construct_yaml_seq)
- 
+
 FullConstructor.add_constructor(
-    'tag:yaml.org,2002:python/tuple', 
+    'tag:yaml.org,2002:python/tuple',
     FullConstructor.construct_python_tuple)
- 
+
 FullConstructor.add_constructor(
-    'tag:yaml.org,2002:python/dict', 
+    'tag:yaml.org,2002:python/dict',
     FullConstructor.construct_yaml_map)
- 
+
 FullConstructor.add_multi_constructor(
-    'tag:yaml.org,2002:python/name:', 
+    'tag:yaml.org,2002:python/name:',
     FullConstructor.construct_python_name)
- 
+
 class UnsafeConstructor(FullConstructor):
 
     def find_python_module(self, name, mark):
diff --git a/contrib/python/PyYAML/py3/yaml/cyaml.py b/contrib/python/PyYAML/py3/yaml/cyaml.py
index 9f7a3e86cf..0c21345879 100644
--- a/contrib/python/PyYAML/py3/yaml/cyaml.py
+++ b/contrib/python/PyYAML/py3/yaml/cyaml.py
@@ -1,32 +1,32 @@
- 
+
 __all__ = [
     'CBaseLoader', 'CSafeLoader', 'CFullLoader', 'CUnsafeLoader', 'CLoader',
     'CBaseDumper', 'CSafeDumper', 'CDumper'
 ]
- 
+
 from yaml._yaml import CParser, CEmitter
- 
-from .constructor import * 
- 
-from .serializer import * 
-from .representer import * 
- 
-from .resolver import * 
- 
-class CBaseLoader(CParser, BaseConstructor, BaseResolver): 
- 
-    def __init__(self, stream): 
-        CParser.__init__(self, stream) 
-        BaseConstructor.__init__(self) 
-        BaseResolver.__init__(self) 
- 
-class CSafeLoader(CParser, SafeConstructor, Resolver): 
- 
-    def __init__(self, stream): 
-        CParser.__init__(self, stream) 
-        SafeConstructor.__init__(self) 
-        Resolver.__init__(self) 
- 
+
+from .constructor import *
+
+from .serializer import *
+from .representer import *
+
+from .resolver import *
+
+class CBaseLoader(CParser, BaseConstructor, BaseResolver):
+
+    def __init__(self, stream):
+        CParser.__init__(self, stream)
+        BaseConstructor.__init__(self)
+        BaseResolver.__init__(self)
+
+class CSafeLoader(CParser, SafeConstructor, Resolver):
+
+    def __init__(self, stream):
+        CParser.__init__(self, stream)
+        SafeConstructor.__init__(self)
+        Resolver.__init__(self)
+
 class CFullLoader(CParser, FullConstructor, Resolver):
 
     def __init__(self, stream):
@@ -41,61 +41,61 @@ class CUnsafeLoader(CParser, UnsafeConstructor, Resolver):
         UnsafeConstructor.__init__(self)
         Resolver.__init__(self)
 
-class CLoader(CParser, Constructor, Resolver): 
- 
-    def __init__(self, stream): 
-        CParser.__init__(self, stream) 
-        Constructor.__init__(self) 
-        Resolver.__init__(self) 
- 
-class CBaseDumper(CEmitter, BaseRepresenter, BaseResolver): 
- 
-    def __init__(self, stream, 
+class CLoader(CParser, Constructor, Resolver):
+
+    def __init__(self, stream):
+        CParser.__init__(self, stream)
+        Constructor.__init__(self)
+        Resolver.__init__(self)
+
+class CBaseDumper(CEmitter, BaseRepresenter, BaseResolver):
+
+    def __init__(self, stream,
             default_style=None, default_flow_style=False,
-            canonical=None, indent=None, width=None, 
-            allow_unicode=None, line_break=None, 
-            encoding=None, explicit_start=None, explicit_end=None, 
+            canonical=None, indent=None, width=None,
+            allow_unicode=None, line_break=None,
+            encoding=None, explicit_start=None, explicit_end=None,
             version=None, tags=None, sort_keys=True):
-        CEmitter.__init__(self, stream, canonical=canonical, 
-                indent=indent, width=width, encoding=encoding, 
-                allow_unicode=allow_unicode, line_break=line_break, 
-                explicit_start=explicit_start, explicit_end=explicit_end, 
-                version=version, tags=tags) 
-        Representer.__init__(self, default_style=default_style, 
+        CEmitter.__init__(self, stream, canonical=canonical,
+                indent=indent, width=width, encoding=encoding,
+                allow_unicode=allow_unicode, line_break=line_break,
+                explicit_start=explicit_start, explicit_end=explicit_end,
+                version=version, tags=tags)
+        Representer.__init__(self, default_style=default_style,
                 default_flow_style=default_flow_style, sort_keys=sort_keys)
-        Resolver.__init__(self) 
- 
-class CSafeDumper(CEmitter, SafeRepresenter, Resolver): 
- 
-    def __init__(self, stream, 
+        Resolver.__init__(self)
+
+class CSafeDumper(CEmitter, SafeRepresenter, Resolver):
+
+    def __init__(self, stream,
             default_style=None, default_flow_style=False,
-            canonical=None, indent=None, width=None, 
-            allow_unicode=None, line_break=None, 
-            encoding=None, explicit_start=None, explicit_end=None, 
+            canonical=None, indent=None, width=None,
+            allow_unicode=None, line_break=None,
+            encoding=None, explicit_start=None, explicit_end=None,
             version=None, tags=None, sort_keys=True):
-        CEmitter.__init__(self, stream, canonical=canonical, 
-                indent=indent, width=width, encoding=encoding, 
-                allow_unicode=allow_unicode, line_break=line_break, 
-                explicit_start=explicit_start, explicit_end=explicit_end, 
-                version=version, tags=tags) 
-        SafeRepresenter.__init__(self, default_style=default_style, 
+        CEmitter.__init__(self, stream, canonical=canonical,
+                indent=indent, width=width, encoding=encoding,
+                allow_unicode=allow_unicode, line_break=line_break,
+                explicit_start=explicit_start, explicit_end=explicit_end,
+                version=version, tags=tags)
+        SafeRepresenter.__init__(self, default_style=default_style,
                 default_flow_style=default_flow_style, sort_keys=sort_keys)
-        Resolver.__init__(self) 
- 
-class CDumper(CEmitter, Serializer, Representer, Resolver): 
- 
-    def __init__(self, stream, 
+        Resolver.__init__(self)
+
+class CDumper(CEmitter, Serializer, Representer, Resolver):
+
+    def __init__(self, stream,
             default_style=None, default_flow_style=False,
-            canonical=None, indent=None, width=None, 
-            allow_unicode=None, line_break=None, 
-            encoding=None, explicit_start=None, explicit_end=None, 
+            canonical=None, indent=None, width=None,
+            allow_unicode=None, line_break=None,
+            encoding=None, explicit_start=None, explicit_end=None,
             version=None, tags=None, sort_keys=True):
-        CEmitter.__init__(self, stream, canonical=canonical, 
-                indent=indent, width=width, encoding=encoding, 
-                allow_unicode=allow_unicode, line_break=line_break, 
-                explicit_start=explicit_start, explicit_end=explicit_end, 
-                version=version, tags=tags) 
-        Representer.__init__(self, default_style=default_style, 
+        CEmitter.__init__(self, stream, canonical=canonical,
+                indent=indent, width=width, encoding=encoding,
+                allow_unicode=allow_unicode, line_break=line_break,
+                explicit_start=explicit_start, explicit_end=explicit_end,
+                version=version, tags=tags)
+        Representer.__init__(self, default_style=default_style,
                 default_flow_style=default_flow_style, sort_keys=sort_keys)
-        Resolver.__init__(self) 
- 
+        Resolver.__init__(self)
+
diff --git a/contrib/python/PyYAML/py3/yaml/dumper.py b/contrib/python/PyYAML/py3/yaml/dumper.py
index 270fce56e1..6aadba551f 100644
--- a/contrib/python/PyYAML/py3/yaml/dumper.py
+++ b/contrib/python/PyYAML/py3/yaml/dumper.py
@@ -1,62 +1,62 @@
- 
-__all__ = ['BaseDumper', 'SafeDumper', 'Dumper'] 
- 
-from .emitter import * 
-from .serializer import * 
-from .representer import * 
-from .resolver import * 
- 
-class BaseDumper(Emitter, Serializer, BaseRepresenter, BaseResolver): 
- 
-    def __init__(self, stream, 
+
+__all__ = ['BaseDumper', 'SafeDumper', 'Dumper']
+
+from .emitter import *
+from .serializer import *
+from .representer import *
+from .resolver import *
+
+class BaseDumper(Emitter, Serializer, BaseRepresenter, BaseResolver):
+
+    def __init__(self, stream,
             default_style=None, default_flow_style=False,
-            canonical=None, indent=None, width=None, 
-            allow_unicode=None, line_break=None, 
-            encoding=None, explicit_start=None, explicit_end=None, 
+            canonical=None, indent=None, width=None,
+            allow_unicode=None, line_break=None,
+            encoding=None, explicit_start=None, explicit_end=None,
             version=None, tags=None, sort_keys=True):
-        Emitter.__init__(self, stream, canonical=canonical, 
-                indent=indent, width=width, 
-                allow_unicode=allow_unicode, line_break=line_break) 
-        Serializer.__init__(self, encoding=encoding, 
-                explicit_start=explicit_start, explicit_end=explicit_end, 
-                version=version, tags=tags) 
-        Representer.__init__(self, default_style=default_style, 
+        Emitter.__init__(self, stream, canonical=canonical,
+                indent=indent, width=width,
+                allow_unicode=allow_unicode, line_break=line_break)
+        Serializer.__init__(self, encoding=encoding,
+                explicit_start=explicit_start, explicit_end=explicit_end,
+                version=version, tags=tags)
+        Representer.__init__(self, default_style=default_style,
                 default_flow_style=default_flow_style, sort_keys=sort_keys)
-        Resolver.__init__(self) 
- 
-class SafeDumper(Emitter, Serializer, SafeRepresenter, Resolver): 
- 
-    def __init__(self, stream, 
+        Resolver.__init__(self)
+
+class SafeDumper(Emitter, Serializer, SafeRepresenter, Resolver):
+
+    def __init__(self, stream,
             default_style=None, default_flow_style=False,
-            canonical=None, indent=None, width=None, 
-            allow_unicode=None, line_break=None, 
-            encoding=None, explicit_start=None, explicit_end=None, 
+            canonical=None, indent=None, width=None,
+            allow_unicode=None, line_break=None,
+            encoding=None, explicit_start=None, explicit_end=None,
             version=None, tags=None, sort_keys=True):
-        Emitter.__init__(self, stream, canonical=canonical, 
-                indent=indent, width=width, 
-                allow_unicode=allow_unicode, line_break=line_break) 
-        Serializer.__init__(self, encoding=encoding, 
-                explicit_start=explicit_start, explicit_end=explicit_end, 
-                version=version, tags=tags) 
-        SafeRepresenter.__init__(self, default_style=default_style, 
+        Emitter.__init__(self, stream, canonical=canonical,
+                indent=indent, width=width,
+                allow_unicode=allow_unicode, line_break=line_break)
+        Serializer.__init__(self, encoding=encoding,
+                explicit_start=explicit_start, explicit_end=explicit_end,
+                version=version, tags=tags)
+        SafeRepresenter.__init__(self, default_style=default_style,
                 default_flow_style=default_flow_style, sort_keys=sort_keys)
-        Resolver.__init__(self) 
- 
-class Dumper(Emitter, Serializer, Representer, Resolver): 
- 
-    def __init__(self, stream, 
+        Resolver.__init__(self)
+
+class Dumper(Emitter, Serializer, Representer, Resolver):
+
+    def __init__(self, stream,
             default_style=None, default_flow_style=False,
-            canonical=None, indent=None, width=None, 
-            allow_unicode=None, line_break=None, 
-            encoding=None, explicit_start=None, explicit_end=None, 
+            canonical=None, indent=None, width=None,
+            allow_unicode=None, line_break=None,
+            encoding=None, explicit_start=None, explicit_end=None,
             version=None, tags=None, sort_keys=True):
-        Emitter.__init__(self, stream, canonical=canonical, 
-                indent=indent, width=width, 
-                allow_unicode=allow_unicode, line_break=line_break) 
-        Serializer.__init__(self, encoding=encoding, 
-                explicit_start=explicit_start, explicit_end=explicit_end, 
-                version=version, tags=tags) 
-        Representer.__init__(self, default_style=default_style, 
+        Emitter.__init__(self, stream, canonical=canonical,
+                indent=indent, width=width,
+                allow_unicode=allow_unicode, line_break=line_break)
+        Serializer.__init__(self, encoding=encoding,
+                explicit_start=explicit_start, explicit_end=explicit_end,
+                version=version, tags=tags)
+        Representer.__init__(self, default_style=default_style,
                 default_flow_style=default_flow_style, sort_keys=sort_keys)
-        Resolver.__init__(self) 
- 
+        Resolver.__init__(self)
+
diff --git a/contrib/python/PyYAML/py3/yaml/emitter.py b/contrib/python/PyYAML/py3/yaml/emitter.py
index e45ee13a3d..a664d01116 100644
--- a/contrib/python/PyYAML/py3/yaml/emitter.py
+++ b/contrib/python/PyYAML/py3/yaml/emitter.py
@@ -1,1137 +1,1137 @@
- 
-# Emitter expects events obeying the following grammar: 
-# stream ::= STREAM-START document* STREAM-END 
-# document ::= DOCUMENT-START node DOCUMENT-END 
-# node ::= SCALAR | sequence | mapping 
-# sequence ::= SEQUENCE-START node* SEQUENCE-END 
-# mapping ::= MAPPING-START (node node)* MAPPING-END 
- 
-__all__ = ['Emitter', 'EmitterError'] 
- 
-from .error import YAMLError 
-from .events import * 
- 
-class EmitterError(YAMLError): 
-    pass 
- 
-class ScalarAnalysis: 
-    def __init__(self, scalar, empty, multiline, 
-            allow_flow_plain, allow_block_plain, 
-            allow_single_quoted, allow_double_quoted, 
-            allow_block): 
-        self.scalar = scalar 
-        self.empty = empty 
-        self.multiline = multiline 
-        self.allow_flow_plain = allow_flow_plain 
-        self.allow_block_plain = allow_block_plain 
-        self.allow_single_quoted = allow_single_quoted 
-        self.allow_double_quoted = allow_double_quoted 
-        self.allow_block = allow_block 
- 
-class Emitter: 
- 
-    DEFAULT_TAG_PREFIXES = { 
-        '!' : '!', 
-        'tag:yaml.org,2002:' : '!!', 
-    } 
- 
-    def __init__(self, stream, canonical=None, indent=None, width=None, 
-            allow_unicode=None, line_break=None): 
- 
-        # The stream should have the methods `write` and possibly `flush`. 
-        self.stream = stream 
- 
+
+# Emitter expects events obeying the following grammar:
+# stream ::= STREAM-START document* STREAM-END
+# document ::= DOCUMENT-START node DOCUMENT-END
+# node ::= SCALAR | sequence | mapping
+# sequence ::= SEQUENCE-START node* SEQUENCE-END
+# mapping ::= MAPPING-START (node node)* MAPPING-END
+
+__all__ = ['Emitter', 'EmitterError']
+
+from .error import YAMLError
+from .events import *
+
+class EmitterError(YAMLError):
+    pass
+
+class ScalarAnalysis:
+    def __init__(self, scalar, empty, multiline,
+            allow_flow_plain, allow_block_plain,
+            allow_single_quoted, allow_double_quoted,
+            allow_block):
+        self.scalar = scalar
+        self.empty = empty
+        self.multiline = multiline
+        self.allow_flow_plain = allow_flow_plain
+        self.allow_block_plain = allow_block_plain
+        self.allow_single_quoted = allow_single_quoted
+        self.allow_double_quoted = allow_double_quoted
+        self.allow_block = allow_block
+
+class Emitter:
+
+    DEFAULT_TAG_PREFIXES = {
+        '!' : '!',
+        'tag:yaml.org,2002:' : '!!',
+    }
+
+    def __init__(self, stream, canonical=None, indent=None, width=None,
+            allow_unicode=None, line_break=None):
+
+        # The stream should have the methods `write` and possibly `flush`.
+        self.stream = stream
+
         # Encoding can be overridden by STREAM-START.
-        self.encoding = None 
- 
-        # Emitter is a state machine with a stack of states to handle nested 
-        # structures. 
-        self.states = [] 
-        self.state = self.expect_stream_start 
- 
-        # Current event and the event queue. 
-        self.events = [] 
-        self.event = None 
- 
-        # The current indentation level and the stack of previous indents. 
-        self.indents = [] 
-        self.indent = None 
- 
-        # Flow level. 
-        self.flow_level = 0 
- 
-        # Contexts. 
-        self.root_context = False 
-        self.sequence_context = False 
-        self.mapping_context = False 
-        self.simple_key_context = False 
- 
-        # Characteristics of the last emitted character: 
-        #  - current position. 
-        #  - is it a whitespace? 
-        #  - is it an indention character 
-        #    (indentation space, '-', '?', or ':')? 
-        self.line = 0 
-        self.column = 0 
-        self.whitespace = True 
-        self.indention = True 
- 
-        # Whether the document requires an explicit document indicator 
-        self.open_ended = False 
- 
-        # Formatting details. 
-        self.canonical = canonical 
-        self.allow_unicode = allow_unicode 
-        self.best_indent = 2 
-        if indent and 1 < indent < 10: 
-            self.best_indent = indent 
-        self.best_width = 80 
-        if width and width > self.best_indent*2: 
-            self.best_width = width 
-        self.best_line_break = '\n' 
-        if line_break in ['\r', '\n', '\r\n']: 
-            self.best_line_break = line_break 
- 
-        # Tag prefixes. 
-        self.tag_prefixes = None 
- 
-        # Prepared anchor and tag. 
-        self.prepared_anchor = None 
-        self.prepared_tag = None 
- 
-        # Scalar analysis and style. 
-        self.analysis = None 
-        self.style = None 
- 
-    def dispose(self): 
-        # Reset the state attributes (to clear self-references) 
-        self.states = [] 
-        self.state = None 
- 
-    def emit(self, event): 
-        self.events.append(event) 
-        while not self.need_more_events(): 
-            self.event = self.events.pop(0) 
-            self.state() 
-            self.event = None 
- 
-    # In some cases, we wait for a few next events before emitting. 
- 
-    def need_more_events(self): 
-        if not self.events: 
-            return True 
-        event = self.events[0] 
-        if isinstance(event, DocumentStartEvent): 
-            return self.need_events(1) 
-        elif isinstance(event, SequenceStartEvent): 
-            return self.need_events(2) 
-        elif isinstance(event, MappingStartEvent): 
-            return self.need_events(3) 
-        else: 
-            return False 
- 
-    def need_events(self, count): 
-        level = 0 
-        for event in self.events[1:]: 
-            if isinstance(event, (DocumentStartEvent, CollectionStartEvent)): 
-                level += 1 
-            elif isinstance(event, (DocumentEndEvent, CollectionEndEvent)): 
-                level -= 1 
-            elif isinstance(event, StreamEndEvent): 
-                level = -1 
-            if level < 0: 
-                return False 
-        return (len(self.events) < count+1) 
- 
-    def increase_indent(self, flow=False, indentless=False): 
-        self.indents.append(self.indent) 
-        if self.indent is None: 
-            if flow: 
-                self.indent = self.best_indent 
-            else: 
-                self.indent = 0 
-        elif not indentless: 
-            self.indent += self.best_indent 
- 
-    # States. 
- 
-    # Stream handlers. 
- 
-    def expect_stream_start(self): 
-        if isinstance(self.event, StreamStartEvent): 
-            if self.event.encoding and not hasattr(self.stream, 'encoding'): 
-                self.encoding = self.event.encoding 
-            self.write_stream_start() 
-            self.state = self.expect_first_document_start 
-        else: 
-            raise EmitterError("expected StreamStartEvent, but got %s" 
-                    % self.event) 
- 
-    def expect_nothing(self): 
-        raise EmitterError("expected nothing, but got %s" % self.event) 
- 
-    # Document handlers. 
- 
-    def expect_first_document_start(self): 
-        return self.expect_document_start(first=True) 
- 
-    def expect_document_start(self, first=False): 
-        if isinstance(self.event, DocumentStartEvent): 
-            if (self.event.version or self.event.tags) and self.open_ended: 
-                self.write_indicator('...', True) 
-                self.write_indent() 
-            if self.event.version: 
-                version_text = self.prepare_version(self.event.version) 
-                self.write_version_directive(version_text) 
-            self.tag_prefixes = self.DEFAULT_TAG_PREFIXES.copy() 
-            if self.event.tags: 
-                handles = sorted(self.event.tags.keys()) 
-                for handle in handles: 
-                    prefix = self.event.tags[handle] 
-                    self.tag_prefixes[prefix] = handle 
-                    handle_text = self.prepare_tag_handle(handle) 
-                    prefix_text = self.prepare_tag_prefix(prefix) 
-                    self.write_tag_directive(handle_text, prefix_text) 
-            implicit = (first and not self.event.explicit and not self.canonical 
-                    and not self.event.version and not self.event.tags 
-                    and not self.check_empty_document()) 
-            if not implicit: 
-                self.write_indent() 
-                self.write_indicator('---', True) 
-                if self.canonical: 
-                    self.write_indent() 
-            self.state = self.expect_document_root 
-        elif isinstance(self.event, StreamEndEvent): 
-            if self.open_ended: 
-                self.write_indicator('...', True) 
-                self.write_indent() 
-            self.write_stream_end() 
-            self.state = self.expect_nothing 
-        else: 
-            raise EmitterError("expected DocumentStartEvent, but got %s" 
-                    % self.event) 
- 
-    def expect_document_end(self): 
-        if isinstance(self.event, DocumentEndEvent): 
-            self.write_indent() 
-            if self.event.explicit: 
-                self.write_indicator('...', True) 
-                self.write_indent() 
-            self.flush_stream() 
-            self.state = self.expect_document_start 
-        else: 
-            raise EmitterError("expected DocumentEndEvent, but got %s" 
-                    % self.event) 
- 
-    def expect_document_root(self): 
-        self.states.append(self.expect_document_end) 
-        self.expect_node(root=True) 
- 
-    # Node handlers. 
- 
-    def expect_node(self, root=False, sequence=False, mapping=False, 
-            simple_key=False): 
-        self.root_context = root 
-        self.sequence_context = sequence 
-        self.mapping_context = mapping 
-        self.simple_key_context = simple_key 
-        if isinstance(self.event, AliasEvent): 
-            self.expect_alias() 
-        elif isinstance(self.event, (ScalarEvent, CollectionStartEvent)): 
-            self.process_anchor('&') 
-            self.process_tag() 
-            if isinstance(self.event, ScalarEvent): 
-                self.expect_scalar() 
-            elif isinstance(self.event, SequenceStartEvent): 
-                if self.flow_level or self.canonical or self.event.flow_style   \ 
-                        or self.check_empty_sequence(): 
-                    self.expect_flow_sequence() 
-                else: 
-                    self.expect_block_sequence() 
-            elif isinstance(self.event, MappingStartEvent): 
-                if self.flow_level or self.canonical or self.event.flow_style   \ 
-                        or self.check_empty_mapping(): 
-                    self.expect_flow_mapping() 
-                else: 
-                    self.expect_block_mapping() 
-        else: 
-            raise EmitterError("expected NodeEvent, but got %s" % self.event) 
- 
-    def expect_alias(self): 
-        if self.event.anchor is None: 
-            raise EmitterError("anchor is not specified for alias") 
-        self.process_anchor('*') 
-        self.state = self.states.pop() 
- 
-    def expect_scalar(self): 
-        self.increase_indent(flow=True) 
-        self.process_scalar() 
-        self.indent = self.indents.pop() 
-        self.state = self.states.pop() 
- 
-    # Flow sequence handlers. 
- 
-    def expect_flow_sequence(self): 
-        self.write_indicator('[', True, whitespace=True) 
-        self.flow_level += 1 
-        self.increase_indent(flow=True) 
-        self.state = self.expect_first_flow_sequence_item 
- 
-    def expect_first_flow_sequence_item(self): 
-        if isinstance(self.event, SequenceEndEvent): 
-            self.indent = self.indents.pop() 
-            self.flow_level -= 1 
-            self.write_indicator(']', False) 
-            self.state = self.states.pop() 
-        else: 
-            if self.canonical or self.column > self.best_width: 
-                self.write_indent() 
-            self.states.append(self.expect_flow_sequence_item) 
-            self.expect_node(sequence=True) 
- 
-    def expect_flow_sequence_item(self): 
-        if isinstance(self.event, SequenceEndEvent): 
-            self.indent = self.indents.pop() 
-            self.flow_level -= 1 
-            if self.canonical: 
-                self.write_indicator(',', False) 
-                self.write_indent() 
-            self.write_indicator(']', False) 
-            self.state = self.states.pop() 
-        else: 
-            self.write_indicator(',', False) 
-            if self.canonical or self.column > self.best_width: 
-                self.write_indent() 
-            self.states.append(self.expect_flow_sequence_item) 
-            self.expect_node(sequence=True) 
- 
-    # Flow mapping handlers. 
- 
-    def expect_flow_mapping(self): 
-        self.write_indicator('{', True, whitespace=True) 
-        self.flow_level += 1 
-        self.increase_indent(flow=True) 
-        self.state = self.expect_first_flow_mapping_key 
- 
-    def expect_first_flow_mapping_key(self): 
-        if isinstance(self.event, MappingEndEvent): 
-            self.indent = self.indents.pop() 
-            self.flow_level -= 1 
-            self.write_indicator('}', False) 
-            self.state = self.states.pop() 
-        else: 
-            if self.canonical or self.column > self.best_width: 
-                self.write_indent() 
-            if not self.canonical and self.check_simple_key(): 
-                self.states.append(self.expect_flow_mapping_simple_value) 
-                self.expect_node(mapping=True, simple_key=True) 
-            else: 
-                self.write_indicator('?', True) 
-                self.states.append(self.expect_flow_mapping_value) 
-                self.expect_node(mapping=True) 
- 
-    def expect_flow_mapping_key(self): 
-        if isinstance(self.event, MappingEndEvent): 
-            self.indent = self.indents.pop() 
-            self.flow_level -= 1 
-            if self.canonical: 
-                self.write_indicator(',', False) 
-                self.write_indent() 
-            self.write_indicator('}', False) 
-            self.state = self.states.pop() 
-        else: 
-            self.write_indicator(',', False) 
-            if self.canonical or self.column > self.best_width: 
-                self.write_indent() 
-            if not self.canonical and self.check_simple_key(): 
-                self.states.append(self.expect_flow_mapping_simple_value) 
-                self.expect_node(mapping=True, simple_key=True) 
-            else: 
-                self.write_indicator('?', True) 
-                self.states.append(self.expect_flow_mapping_value) 
-                self.expect_node(mapping=True) 
- 
-    def expect_flow_mapping_simple_value(self): 
-        self.write_indicator(':', False) 
-        self.states.append(self.expect_flow_mapping_key) 
-        self.expect_node(mapping=True) 
- 
-    def expect_flow_mapping_value(self): 
-        if self.canonical or self.column > self.best_width: 
-            self.write_indent() 
-        self.write_indicator(':', True) 
-        self.states.append(self.expect_flow_mapping_key) 
-        self.expect_node(mapping=True) 
- 
-    # Block sequence handlers. 
- 
-    def expect_block_sequence(self): 
-        indentless = (self.mapping_context and not self.indention) 
-        self.increase_indent(flow=False, indentless=indentless) 
-        self.state = self.expect_first_block_sequence_item 
- 
-    def expect_first_block_sequence_item(self): 
-        return self.expect_block_sequence_item(first=True) 
- 
-    def expect_block_sequence_item(self, first=False): 
-        if not first and isinstance(self.event, SequenceEndEvent): 
-            self.indent = self.indents.pop() 
-            self.state = self.states.pop() 
-        else: 
-            self.write_indent() 
-            self.write_indicator('-', True, indention=True) 
-            self.states.append(self.expect_block_sequence_item) 
-            self.expect_node(sequence=True) 
- 
-    # Block mapping handlers. 
- 
-    def expect_block_mapping(self): 
-        self.increase_indent(flow=False) 
-        self.state = self.expect_first_block_mapping_key 
- 
-    def expect_first_block_mapping_key(self): 
-        return self.expect_block_mapping_key(first=True) 
- 
-    def expect_block_mapping_key(self, first=False): 
-        if not first and isinstance(self.event, MappingEndEvent): 
-            self.indent = self.indents.pop() 
-            self.state = self.states.pop() 
-        else: 
-            self.write_indent() 
-            if self.check_simple_key(): 
-                self.states.append(self.expect_block_mapping_simple_value) 
-                self.expect_node(mapping=True, simple_key=True) 
-            else: 
-                self.write_indicator('?', True, indention=True) 
-                self.states.append(self.expect_block_mapping_value) 
-                self.expect_node(mapping=True) 
- 
-    def expect_block_mapping_simple_value(self): 
-        self.write_indicator(':', False) 
-        self.states.append(self.expect_block_mapping_key) 
-        self.expect_node(mapping=True) 
- 
-    def expect_block_mapping_value(self): 
-        self.write_indent() 
-        self.write_indicator(':', True, indention=True) 
-        self.states.append(self.expect_block_mapping_key) 
-        self.expect_node(mapping=True) 
- 
-    # Checkers. 
- 
-    def check_empty_sequence(self): 
-        return (isinstance(self.event, SequenceStartEvent) and self.events 
-                and isinstance(self.events[0], SequenceEndEvent)) 
- 
-    def check_empty_mapping(self): 
-        return (isinstance(self.event, MappingStartEvent) and self.events 
-                and isinstance(self.events[0], MappingEndEvent)) 
- 
-    def check_empty_document(self): 
-        if not isinstance(self.event, DocumentStartEvent) or not self.events: 
-            return False 
-        event = self.events[0] 
-        return (isinstance(event, ScalarEvent) and event.anchor is None 
-                and event.tag is None and event.implicit and event.value == '') 
- 
-    def check_simple_key(self): 
-        length = 0 
-        if isinstance(self.event, NodeEvent) and self.event.anchor is not None: 
-            if self.prepared_anchor is None: 
-                self.prepared_anchor = self.prepare_anchor(self.event.anchor) 
-            length += len(self.prepared_anchor) 
-        if isinstance(self.event, (ScalarEvent, CollectionStartEvent))  \ 
-                and self.event.tag is not None: 
-            if self.prepared_tag is None: 
-                self.prepared_tag = self.prepare_tag(self.event.tag) 
-            length += len(self.prepared_tag) 
-        if isinstance(self.event, ScalarEvent): 
-            if self.analysis is None: 
-                self.analysis = self.analyze_scalar(self.event.value) 
-            length += len(self.analysis.scalar) 
-        return (length < 128 and (isinstance(self.event, AliasEvent) 
-            or (isinstance(self.event, ScalarEvent) 
-                    and not self.analysis.empty and not self.analysis.multiline) 
-            or self.check_empty_sequence() or self.check_empty_mapping())) 
- 
-    # Anchor, Tag, and Scalar processors. 
- 
-    def process_anchor(self, indicator): 
-        if self.event.anchor is None: 
-            self.prepared_anchor = None 
-            return 
-        if self.prepared_anchor is None: 
-            self.prepared_anchor = self.prepare_anchor(self.event.anchor) 
-        if self.prepared_anchor: 
-            self.write_indicator(indicator+self.prepared_anchor, True) 
-        self.prepared_anchor = None 
- 
-    def process_tag(self): 
-        tag = self.event.tag 
-        if isinstance(self.event, ScalarEvent): 
-            if self.style is None: 
-                self.style = self.choose_scalar_style() 
-            if ((not self.canonical or tag is None) and 
-                ((self.style == '' and self.event.implicit[0]) 
-                        or (self.style != '' and self.event.implicit[1]))): 
-                self.prepared_tag = None 
-                return 
-            if self.event.implicit[0] and tag is None: 
-                tag = '!' 
-                self.prepared_tag = None 
-        else: 
-            if (not self.canonical or tag is None) and self.event.implicit: 
-                self.prepared_tag = None 
-                return 
-        if tag is None: 
-            raise EmitterError("tag is not specified") 
-        if self.prepared_tag is None: 
-            self.prepared_tag = self.prepare_tag(tag) 
-        if self.prepared_tag: 
-            self.write_indicator(self.prepared_tag, True) 
-        self.prepared_tag = None 
- 
-    def choose_scalar_style(self): 
-        if self.analysis is None: 
-            self.analysis = self.analyze_scalar(self.event.value) 
-        if self.event.style == '"' or self.canonical: 
-            return '"' 
-        if not self.event.style and self.event.implicit[0]: 
-            if (not (self.simple_key_context and 
-                    (self.analysis.empty or self.analysis.multiline)) 
-                and (self.flow_level and self.analysis.allow_flow_plain 
-                    or (not self.flow_level and self.analysis.allow_block_plain))): 
-                return '' 
-        if self.event.style and self.event.style in '|>': 
-            if (not self.flow_level and not self.simple_key_context 
-                    and self.analysis.allow_block): 
-                return self.event.style 
-        if not self.event.style or self.event.style == '\'': 
-            if (self.analysis.allow_single_quoted and 
-                    not (self.simple_key_context and self.analysis.multiline)): 
-                return '\'' 
-        return '"' 
- 
-    def process_scalar(self): 
-        if self.analysis is None: 
-            self.analysis = self.analyze_scalar(self.event.value) 
-        if self.style is None: 
-            self.style = self.choose_scalar_style() 
-        split = (not self.simple_key_context) 
-        #if self.analysis.multiline and split    \ 
-        #        and (not self.style or self.style in '\'\"'): 
-        #    self.write_indent() 
-        if self.style == '"': 
-            self.write_double_quoted(self.analysis.scalar, split) 
-        elif self.style == '\'': 
-            self.write_single_quoted(self.analysis.scalar, split) 
-        elif self.style == '>': 
-            self.write_folded(self.analysis.scalar) 
-        elif self.style == '|': 
-            self.write_literal(self.analysis.scalar) 
-        else: 
-            self.write_plain(self.analysis.scalar, split) 
-        self.analysis = None 
-        self.style = None 
- 
-    # Analyzers. 
- 
-    def prepare_version(self, version): 
-        major, minor = version 
-        if major != 1: 
-            raise EmitterError("unsupported YAML version: %d.%d" % (major, minor)) 
-        return '%d.%d' % (major, minor) 
- 
-    def prepare_tag_handle(self, handle): 
-        if not handle: 
-            raise EmitterError("tag handle must not be empty") 
-        if handle[0] != '!' or handle[-1] != '!': 
-            raise EmitterError("tag handle must start and end with '!': %r" % handle) 
-        for ch in handle[1:-1]: 
-            if not ('0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z'    \ 
-                    or ch in '-_'): 
-                raise EmitterError("invalid character %r in the tag handle: %r" 
-                        % (ch, handle)) 
-        return handle 
- 
-    def prepare_tag_prefix(self, prefix): 
-        if not prefix: 
-            raise EmitterError("tag prefix must not be empty") 
-        chunks = [] 
-        start = end = 0 
-        if prefix[0] == '!': 
-            end = 1 
-        while end < len(prefix): 
-            ch = prefix[end] 
-            if '0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z' \ 
-                    or ch in '-;/?!:@&=+$,_.~*\'()[]': 
-                end += 1 
-            else: 
-                if start < end: 
-                    chunks.append(prefix[start:end]) 
-                start = end = end+1 
-                data = ch.encode('utf-8') 
-                for ch in data: 
-                    chunks.append('%%%02X' % ord(ch)) 
-        if start < end: 
-            chunks.append(prefix[start:end]) 
-        return ''.join(chunks) 
- 
-    def prepare_tag(self, tag): 
-        if not tag: 
-            raise EmitterError("tag must not be empty") 
-        if tag == '!': 
-            return tag 
-        handle = None 
-        suffix = tag 
-        prefixes = sorted(self.tag_prefixes.keys()) 
-        for prefix in prefixes: 
-            if tag.startswith(prefix)   \ 
-                    and (prefix == '!' or len(prefix) < len(tag)): 
-                handle = self.tag_prefixes[prefix] 
-                suffix = tag[len(prefix):] 
-        chunks = [] 
-        start = end = 0 
-        while end < len(suffix): 
-            ch = suffix[end] 
-            if '0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z' \ 
-                    or ch in '-;/?:@&=+$,_.~*\'()[]'   \ 
-                    or (ch == '!' and handle != '!'): 
-                end += 1 
-            else: 
-                if start < end: 
-                    chunks.append(suffix[start:end]) 
-                start = end = end+1 
-                data = ch.encode('utf-8') 
-                for ch in data: 
+        self.encoding = None
+
+        # Emitter is a state machine with a stack of states to handle nested
+        # structures.
+        self.states = []
+        self.state = self.expect_stream_start
+
+        # Current event and the event queue.
+        self.events = []
+        self.event = None
+
+        # The current indentation level and the stack of previous indents.
+        self.indents = []
+        self.indent = None
+
+        # Flow level.
+        self.flow_level = 0
+
+        # Contexts.
+        self.root_context = False
+        self.sequence_context = False
+        self.mapping_context = False
+        self.simple_key_context = False
+
+        # Characteristics of the last emitted character:
+        #  - current position.
+        #  - is it a whitespace?
+        #  - is it an indention character
+        #    (indentation space, '-', '?', or ':')?
+        self.line = 0
+        self.column = 0
+        self.whitespace = True
+        self.indention = True
+
+        # Whether the document requires an explicit document indicator
+        self.open_ended = False
+
+        # Formatting details.
+        self.canonical = canonical
+        self.allow_unicode = allow_unicode
+        self.best_indent = 2
+        if indent and 1 < indent < 10:
+            self.best_indent = indent
+        self.best_width = 80
+        if width and width > self.best_indent*2:
+            self.best_width = width
+        self.best_line_break = '\n'
+        if line_break in ['\r', '\n', '\r\n']:
+            self.best_line_break = line_break
+
+        # Tag prefixes.
+        self.tag_prefixes = None
+
+        # Prepared anchor and tag.
+        self.prepared_anchor = None
+        self.prepared_tag = None
+
+        # Scalar analysis and style.
+        self.analysis = None
+        self.style = None
+
+    def dispose(self):
+        # Reset the state attributes (to clear self-references)
+        self.states = []
+        self.state = None
+
+    def emit(self, event):
+        self.events.append(event)
+        while not self.need_more_events():
+            self.event = self.events.pop(0)
+            self.state()
+            self.event = None
+
+    # In some cases, we wait for a few next events before emitting.
+
+    def need_more_events(self):
+        if not self.events:
+            return True
+        event = self.events[0]
+        if isinstance(event, DocumentStartEvent):
+            return self.need_events(1)
+        elif isinstance(event, SequenceStartEvent):
+            return self.need_events(2)
+        elif isinstance(event, MappingStartEvent):
+            return self.need_events(3)
+        else:
+            return False
+
+    def need_events(self, count):
+        level = 0
+        for event in self.events[1:]:
+            if isinstance(event, (DocumentStartEvent, CollectionStartEvent)):
+                level += 1
+            elif isinstance(event, (DocumentEndEvent, CollectionEndEvent)):
+                level -= 1
+            elif isinstance(event, StreamEndEvent):
+                level = -1
+            if level < 0:
+                return False
+        return (len(self.events) < count+1)
+
+    def increase_indent(self, flow=False, indentless=False):
+        self.indents.append(self.indent)
+        if self.indent is None:
+            if flow:
+                self.indent = self.best_indent
+            else:
+                self.indent = 0
+        elif not indentless:
+            self.indent += self.best_indent
+
+    # States.
+
+    # Stream handlers.
+
+    def expect_stream_start(self):
+        if isinstance(self.event, StreamStartEvent):
+            if self.event.encoding and not hasattr(self.stream, 'encoding'):
+                self.encoding = self.event.encoding
+            self.write_stream_start()
+            self.state = self.expect_first_document_start
+        else:
+            raise EmitterError("expected StreamStartEvent, but got %s"
+                    % self.event)
+
+    def expect_nothing(self):
+        raise EmitterError("expected nothing, but got %s" % self.event)
+
+    # Document handlers.
+
+    def expect_first_document_start(self):
+        return self.expect_document_start(first=True)
+
+    def expect_document_start(self, first=False):
+        if isinstance(self.event, DocumentStartEvent):
+            if (self.event.version or self.event.tags) and self.open_ended:
+                self.write_indicator('...', True)
+                self.write_indent()
+            if self.event.version:
+                version_text = self.prepare_version(self.event.version)
+                self.write_version_directive(version_text)
+            self.tag_prefixes = self.DEFAULT_TAG_PREFIXES.copy()
+            if self.event.tags:
+                handles = sorted(self.event.tags.keys())
+                for handle in handles:
+                    prefix = self.event.tags[handle]
+                    self.tag_prefixes[prefix] = handle
+                    handle_text = self.prepare_tag_handle(handle)
+                    prefix_text = self.prepare_tag_prefix(prefix)
+                    self.write_tag_directive(handle_text, prefix_text)
+            implicit = (first and not self.event.explicit and not self.canonical
+                    and not self.event.version and not self.event.tags
+                    and not self.check_empty_document())
+            if not implicit:
+                self.write_indent()
+                self.write_indicator('---', True)
+                if self.canonical:
+                    self.write_indent()
+            self.state = self.expect_document_root
+        elif isinstance(self.event, StreamEndEvent):
+            if self.open_ended:
+                self.write_indicator('...', True)
+                self.write_indent()
+            self.write_stream_end()
+            self.state = self.expect_nothing
+        else:
+            raise EmitterError("expected DocumentStartEvent, but got %s"
+                    % self.event)
+
+    def expect_document_end(self):
+        if isinstance(self.event, DocumentEndEvent):
+            self.write_indent()
+            if self.event.explicit:
+                self.write_indicator('...', True)
+                self.write_indent()
+            self.flush_stream()
+            self.state = self.expect_document_start
+        else:
+            raise EmitterError("expected DocumentEndEvent, but got %s"
+                    % self.event)
+
+    def expect_document_root(self):
+        self.states.append(self.expect_document_end)
+        self.expect_node(root=True)
+
+    # Node handlers.
+
+    def expect_node(self, root=False, sequence=False, mapping=False,
+            simple_key=False):
+        self.root_context = root
+        self.sequence_context = sequence
+        self.mapping_context = mapping
+        self.simple_key_context = simple_key
+        if isinstance(self.event, AliasEvent):
+            self.expect_alias()
+        elif isinstance(self.event, (ScalarEvent, CollectionStartEvent)):
+            self.process_anchor('&')
+            self.process_tag()
+            if isinstance(self.event, ScalarEvent):
+                self.expect_scalar()
+            elif isinstance(self.event, SequenceStartEvent):
+                if self.flow_level or self.canonical or self.event.flow_style   \
+                        or self.check_empty_sequence():
+                    self.expect_flow_sequence()
+                else:
+                    self.expect_block_sequence()
+            elif isinstance(self.event, MappingStartEvent):
+                if self.flow_level or self.canonical or self.event.flow_style   \
+                        or self.check_empty_mapping():
+                    self.expect_flow_mapping()
+                else:
+                    self.expect_block_mapping()
+        else:
+            raise EmitterError("expected NodeEvent, but got %s" % self.event)
+
+    def expect_alias(self):
+        if self.event.anchor is None:
+            raise EmitterError("anchor is not specified for alias")
+        self.process_anchor('*')
+        self.state = self.states.pop()
+
+    def expect_scalar(self):
+        self.increase_indent(flow=True)
+        self.process_scalar()
+        self.indent = self.indents.pop()
+        self.state = self.states.pop()
+
+    # Flow sequence handlers.
+
+    def expect_flow_sequence(self):
+        self.write_indicator('[', True, whitespace=True)
+        self.flow_level += 1
+        self.increase_indent(flow=True)
+        self.state = self.expect_first_flow_sequence_item
+
+    def expect_first_flow_sequence_item(self):
+        if isinstance(self.event, SequenceEndEvent):
+            self.indent = self.indents.pop()
+            self.flow_level -= 1
+            self.write_indicator(']', False)
+            self.state = self.states.pop()
+        else:
+            if self.canonical or self.column > self.best_width:
+                self.write_indent()
+            self.states.append(self.expect_flow_sequence_item)
+            self.expect_node(sequence=True)
+
+    def expect_flow_sequence_item(self):
+        if isinstance(self.event, SequenceEndEvent):
+            self.indent = self.indents.pop()
+            self.flow_level -= 1
+            if self.canonical:
+                self.write_indicator(',', False)
+                self.write_indent()
+            self.write_indicator(']', False)
+            self.state = self.states.pop()
+        else:
+            self.write_indicator(',', False)
+            if self.canonical or self.column > self.best_width:
+                self.write_indent()
+            self.states.append(self.expect_flow_sequence_item)
+            self.expect_node(sequence=True)
+
+    # Flow mapping handlers.
+
+    def expect_flow_mapping(self):
+        self.write_indicator('{', True, whitespace=True)
+        self.flow_level += 1
+        self.increase_indent(flow=True)
+        self.state = self.expect_first_flow_mapping_key
+
+    def expect_first_flow_mapping_key(self):
+        if isinstance(self.event, MappingEndEvent):
+            self.indent = self.indents.pop()
+            self.flow_level -= 1
+            self.write_indicator('}', False)
+            self.state = self.states.pop()
+        else:
+            if self.canonical or self.column > self.best_width:
+                self.write_indent()
+            if not self.canonical and self.check_simple_key():
+                self.states.append(self.expect_flow_mapping_simple_value)
+                self.expect_node(mapping=True, simple_key=True)
+            else:
+                self.write_indicator('?', True)
+                self.states.append(self.expect_flow_mapping_value)
+                self.expect_node(mapping=True)
+
+    def expect_flow_mapping_key(self):
+        if isinstance(self.event, MappingEndEvent):
+            self.indent = self.indents.pop()
+            self.flow_level -= 1
+            if self.canonical:
+                self.write_indicator(',', False)
+                self.write_indent()
+            self.write_indicator('}', False)
+            self.state = self.states.pop()
+        else:
+            self.write_indicator(',', False)
+            if self.canonical or self.column > self.best_width:
+                self.write_indent()
+            if not self.canonical and self.check_simple_key():
+                self.states.append(self.expect_flow_mapping_simple_value)
+                self.expect_node(mapping=True, simple_key=True)
+            else:
+                self.write_indicator('?', True)
+                self.states.append(self.expect_flow_mapping_value)
+                self.expect_node(mapping=True)
+
+    def expect_flow_mapping_simple_value(self):
+        self.write_indicator(':', False)
+        self.states.append(self.expect_flow_mapping_key)
+        self.expect_node(mapping=True)
+
+    def expect_flow_mapping_value(self):
+        if self.canonical or self.column > self.best_width:
+            self.write_indent()
+        self.write_indicator(':', True)
+        self.states.append(self.expect_flow_mapping_key)
+        self.expect_node(mapping=True)
+
+    # Block sequence handlers.
+
+    def expect_block_sequence(self):
+        indentless = (self.mapping_context and not self.indention)
+        self.increase_indent(flow=False, indentless=indentless)
+        self.state = self.expect_first_block_sequence_item
+
+    def expect_first_block_sequence_item(self):
+        return self.expect_block_sequence_item(first=True)
+
+    def expect_block_sequence_item(self, first=False):
+        if not first and isinstance(self.event, SequenceEndEvent):
+            self.indent = self.indents.pop()
+            self.state = self.states.pop()
+        else:
+            self.write_indent()
+            self.write_indicator('-', True, indention=True)
+            self.states.append(self.expect_block_sequence_item)
+            self.expect_node(sequence=True)
+
+    # Block mapping handlers.
+
+    def expect_block_mapping(self):
+        self.increase_indent(flow=False)
+        self.state = self.expect_first_block_mapping_key
+
+    def expect_first_block_mapping_key(self):
+        return self.expect_block_mapping_key(first=True)
+
+    def expect_block_mapping_key(self, first=False):
+        if not first and isinstance(self.event, MappingEndEvent):
+            self.indent = self.indents.pop()
+            self.state = self.states.pop()
+        else:
+            self.write_indent()
+            if self.check_simple_key():
+                self.states.append(self.expect_block_mapping_simple_value)
+                self.expect_node(mapping=True, simple_key=True)
+            else:
+                self.write_indicator('?', True, indention=True)
+                self.states.append(self.expect_block_mapping_value)
+                self.expect_node(mapping=True)
+
+    def expect_block_mapping_simple_value(self):
+        self.write_indicator(':', False)
+        self.states.append(self.expect_block_mapping_key)
+        self.expect_node(mapping=True)
+
+    def expect_block_mapping_value(self):
+        self.write_indent()
+        self.write_indicator(':', True, indention=True)
+        self.states.append(self.expect_block_mapping_key)
+        self.expect_node(mapping=True)
+
+    # Checkers.
+
+    def check_empty_sequence(self):
+        return (isinstance(self.event, SequenceStartEvent) and self.events
+                and isinstance(self.events[0], SequenceEndEvent))
+
+    def check_empty_mapping(self):
+        return (isinstance(self.event, MappingStartEvent) and self.events
+                and isinstance(self.events[0], MappingEndEvent))
+
+    def check_empty_document(self):
+        if not isinstance(self.event, DocumentStartEvent) or not self.events:
+            return False
+        event = self.events[0]
+        return (isinstance(event, ScalarEvent) and event.anchor is None
+                and event.tag is None and event.implicit and event.value == '')
+
+    def check_simple_key(self):
+        length = 0
+        if isinstance(self.event, NodeEvent) and self.event.anchor is not None:
+            if self.prepared_anchor is None:
+                self.prepared_anchor = self.prepare_anchor(self.event.anchor)
+            length += len(self.prepared_anchor)
+        if isinstance(self.event, (ScalarEvent, CollectionStartEvent))  \
+                and self.event.tag is not None:
+            if self.prepared_tag is None:
+                self.prepared_tag = self.prepare_tag(self.event.tag)
+            length += len(self.prepared_tag)
+        if isinstance(self.event, ScalarEvent):
+            if self.analysis is None:
+                self.analysis = self.analyze_scalar(self.event.value)
+            length += len(self.analysis.scalar)
+        return (length < 128 and (isinstance(self.event, AliasEvent)
+            or (isinstance(self.event, ScalarEvent)
+                    and not self.analysis.empty and not self.analysis.multiline)
+            or self.check_empty_sequence() or self.check_empty_mapping()))
+
+    # Anchor, Tag, and Scalar processors.
+
+    def process_anchor(self, indicator):
+        if self.event.anchor is None:
+            self.prepared_anchor = None
+            return
+        if self.prepared_anchor is None:
+            self.prepared_anchor = self.prepare_anchor(self.event.anchor)
+        if self.prepared_anchor:
+            self.write_indicator(indicator+self.prepared_anchor, True)
+        self.prepared_anchor = None
+
+    def process_tag(self):
+        tag = self.event.tag
+        if isinstance(self.event, ScalarEvent):
+            if self.style is None:
+                self.style = self.choose_scalar_style()
+            if ((not self.canonical or tag is None) and
+                ((self.style == '' and self.event.implicit[0])
+                        or (self.style != '' and self.event.implicit[1]))):
+                self.prepared_tag = None
+                return
+            if self.event.implicit[0] and tag is None:
+                tag = '!'
+                self.prepared_tag = None
+        else:
+            if (not self.canonical or tag is None) and self.event.implicit:
+                self.prepared_tag = None
+                return
+        if tag is None:
+            raise EmitterError("tag is not specified")
+        if self.prepared_tag is None:
+            self.prepared_tag = self.prepare_tag(tag)
+        if self.prepared_tag:
+            self.write_indicator(self.prepared_tag, True)
+        self.prepared_tag = None
+
+    def choose_scalar_style(self):
+        if self.analysis is None:
+            self.analysis = self.analyze_scalar(self.event.value)
+        if self.event.style == '"' or self.canonical:
+            return '"'
+        if not self.event.style and self.event.implicit[0]:
+            if (not (self.simple_key_context and
+                    (self.analysis.empty or self.analysis.multiline))
+                and (self.flow_level and self.analysis.allow_flow_plain
+                    or (not self.flow_level and self.analysis.allow_block_plain))):
+                return ''
+        if self.event.style and self.event.style in '|>':
+            if (not self.flow_level and not self.simple_key_context
+                    and self.analysis.allow_block):
+                return self.event.style
+        if not self.event.style or self.event.style == '\'':
+            if (self.analysis.allow_single_quoted and
+                    not (self.simple_key_context and self.analysis.multiline)):
+                return '\''
+        return '"'
+
+    def process_scalar(self):
+        if self.analysis is None:
+            self.analysis = self.analyze_scalar(self.event.value)
+        if self.style is None:
+            self.style = self.choose_scalar_style()
+        split = (not self.simple_key_context)
+        #if self.analysis.multiline and split    \
+        #        and (not self.style or self.style in '\'\"'):
+        #    self.write_indent()
+        if self.style == '"':
+            self.write_double_quoted(self.analysis.scalar, split)
+        elif self.style == '\'':
+            self.write_single_quoted(self.analysis.scalar, split)
+        elif self.style == '>':
+            self.write_folded(self.analysis.scalar)
+        elif self.style == '|':
+            self.write_literal(self.analysis.scalar)
+        else:
+            self.write_plain(self.analysis.scalar, split)
+        self.analysis = None
+        self.style = None
+
+    # Analyzers.
+
+    def prepare_version(self, version):
+        major, minor = version
+        if major != 1:
+            raise EmitterError("unsupported YAML version: %d.%d" % (major, minor))
+        return '%d.%d' % (major, minor)
+
+    def prepare_tag_handle(self, handle):
+        if not handle:
+            raise EmitterError("tag handle must not be empty")
+        if handle[0] != '!' or handle[-1] != '!':
+            raise EmitterError("tag handle must start and end with '!': %r" % handle)
+        for ch in handle[1:-1]:
+            if not ('0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z'    \
+                    or ch in '-_'):
+                raise EmitterError("invalid character %r in the tag handle: %r"
+                        % (ch, handle))
+        return handle
+
+    def prepare_tag_prefix(self, prefix):
+        if not prefix:
+            raise EmitterError("tag prefix must not be empty")
+        chunks = []
+        start = end = 0
+        if prefix[0] == '!':
+            end = 1
+        while end < len(prefix):
+            ch = prefix[end]
+            if '0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z' \
+                    or ch in '-;/?!:@&=+$,_.~*\'()[]':
+                end += 1
+            else:
+                if start < end:
+                    chunks.append(prefix[start:end])
+                start = end = end+1
+                data = ch.encode('utf-8')
+                for ch in data:
+                    chunks.append('%%%02X' % ord(ch))
+        if start < end:
+            chunks.append(prefix[start:end])
+        return ''.join(chunks)
+
+    def prepare_tag(self, tag):
+        if not tag:
+            raise EmitterError("tag must not be empty")
+        if tag == '!':
+            return tag
+        handle = None
+        suffix = tag
+        prefixes = sorted(self.tag_prefixes.keys())
+        for prefix in prefixes:
+            if tag.startswith(prefix)   \
+                    and (prefix == '!' or len(prefix) < len(tag)):
+                handle = self.tag_prefixes[prefix]
+                suffix = tag[len(prefix):]
+        chunks = []
+        start = end = 0
+        while end < len(suffix):
+            ch = suffix[end]
+            if '0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z' \
+                    or ch in '-;/?:@&=+$,_.~*\'()[]'   \
+                    or (ch == '!' and handle != '!'):
+                end += 1
+            else:
+                if start < end:
+                    chunks.append(suffix[start:end])
+                start = end = end+1
+                data = ch.encode('utf-8')
+                for ch in data:
                     chunks.append('%%%02X' % ch)
-        if start < end: 
-            chunks.append(suffix[start:end]) 
-        suffix_text = ''.join(chunks) 
-        if handle: 
-            return '%s%s' % (handle, suffix_text) 
-        else: 
-            return '!<%s>' % suffix_text 
- 
-    def prepare_anchor(self, anchor): 
-        if not anchor: 
-            raise EmitterError("anchor must not be empty") 
-        for ch in anchor: 
-            if not ('0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z'    \ 
-                    or ch in '-_'): 
-                raise EmitterError("invalid character %r in the anchor: %r" 
-                        % (ch, anchor)) 
-        return anchor 
- 
-    def analyze_scalar(self, scalar): 
- 
-        # Empty scalar is a special case. 
-        if not scalar: 
-            return ScalarAnalysis(scalar=scalar, empty=True, multiline=False, 
-                    allow_flow_plain=False, allow_block_plain=True, 
-                    allow_single_quoted=True, allow_double_quoted=True, 
-                    allow_block=False) 
- 
-        # Indicators and special characters. 
-        block_indicators = False 
-        flow_indicators = False 
-        line_breaks = False 
-        special_characters = False 
- 
-        # Important whitespace combinations. 
-        leading_space = False 
-        leading_break = False 
-        trailing_space = False 
-        trailing_break = False 
-        break_space = False 
-        space_break = False 
- 
-        # Check document indicators. 
-        if scalar.startswith('---') or scalar.startswith('...'): 
-            block_indicators = True 
-            flow_indicators = True 
- 
-        # First character or preceded by a whitespace. 
+        if start < end:
+            chunks.append(suffix[start:end])
+        suffix_text = ''.join(chunks)
+        if handle:
+            return '%s%s' % (handle, suffix_text)
+        else:
+            return '!<%s>' % suffix_text
+
+    def prepare_anchor(self, anchor):
+        if not anchor:
+            raise EmitterError("anchor must not be empty")
+        for ch in anchor:
+            if not ('0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z'    \
+                    or ch in '-_'):
+                raise EmitterError("invalid character %r in the anchor: %r"
+                        % (ch, anchor))
+        return anchor
+
+    def analyze_scalar(self, scalar):
+
+        # Empty scalar is a special case.
+        if not scalar:
+            return ScalarAnalysis(scalar=scalar, empty=True, multiline=False,
+                    allow_flow_plain=False, allow_block_plain=True,
+                    allow_single_quoted=True, allow_double_quoted=True,
+                    allow_block=False)
+
+        # Indicators and special characters.
+        block_indicators = False
+        flow_indicators = False
+        line_breaks = False
+        special_characters = False
+
+        # Important whitespace combinations.
+        leading_space = False
+        leading_break = False
+        trailing_space = False
+        trailing_break = False
+        break_space = False
+        space_break = False
+
+        # Check document indicators.
+        if scalar.startswith('---') or scalar.startswith('...'):
+            block_indicators = True
+            flow_indicators = True
+
+        # First character or preceded by a whitespace.
         preceded_by_whitespace = True
- 
-        # Last character or followed by a whitespace. 
-        followed_by_whitespace = (len(scalar) == 1 or 
-                scalar[1] in '\0 \t\r\n\x85\u2028\u2029') 
- 
-        # The previous character is a space. 
-        previous_space = False 
- 
-        # The previous character is a break. 
-        previous_break = False 
- 
-        index = 0 
-        while index < len(scalar): 
-            ch = scalar[index] 
- 
-            # Check for indicators. 
-            if index == 0: 
-                # Leading indicators are special characters. 
+
+        # Last character or followed by a whitespace.
+        followed_by_whitespace = (len(scalar) == 1 or
+                scalar[1] in '\0 \t\r\n\x85\u2028\u2029')
+
+        # The previous character is a space.
+        previous_space = False
+
+        # The previous character is a break.
+        previous_break = False
+
+        index = 0
+        while index < len(scalar):
+            ch = scalar[index]
+
+            # Check for indicators.
+            if index == 0:
+                # Leading indicators are special characters.
                 if ch in '#,[]{}&*!|>\'\"%@`':
-                    flow_indicators = True 
-                    block_indicators = True 
-                if ch in '?:': 
-                    flow_indicators = True 
-                    if followed_by_whitespace: 
-                        block_indicators = True 
-                if ch == '-' and followed_by_whitespace: 
-                    flow_indicators = True 
-                    block_indicators = True 
-            else: 
-                # Some indicators cannot appear within a scalar as well. 
-                if ch in ',?[]{}': 
-                    flow_indicators = True 
-                if ch == ':': 
-                    flow_indicators = True 
-                    if followed_by_whitespace: 
-                        block_indicators = True 
+                    flow_indicators = True
+                    block_indicators = True
+                if ch in '?:':
+                    flow_indicators = True
+                    if followed_by_whitespace:
+                        block_indicators = True
+                if ch == '-' and followed_by_whitespace:
+                    flow_indicators = True
+                    block_indicators = True
+            else:
+                # Some indicators cannot appear within a scalar as well.
+                if ch in ',?[]{}':
+                    flow_indicators = True
+                if ch == ':':
+                    flow_indicators = True
+                    if followed_by_whitespace:
+                        block_indicators = True
                 if ch == '#' and preceded_by_whitespace:
-                    flow_indicators = True 
-                    block_indicators = True 
- 
-            # Check for line breaks, special, and unicode characters. 
-            if ch in '\n\x85\u2028\u2029': 
-                line_breaks = True 
-            if not (ch == '\n' or '\x20' <= ch <= '\x7E'): 
-                if (ch == '\x85' or '\xA0' <= ch <= '\uD7FF' 
+                    flow_indicators = True
+                    block_indicators = True
+
+            # Check for line breaks, special, and unicode characters.
+            if ch in '\n\x85\u2028\u2029':
+                line_breaks = True
+            if not (ch == '\n' or '\x20' <= ch <= '\x7E'):
+                if (ch == '\x85' or '\xA0' <= ch <= '\uD7FF'
                         or '\uE000' <= ch <= '\uFFFD'
                         or '\U00010000' <= ch < '\U0010ffff') and ch != '\uFEFF':
-                    unicode_characters = True 
-                    if not self.allow_unicode: 
-                        special_characters = True 
-                else: 
-                    special_characters = True 
- 
-            # Detect important whitespace combinations. 
-            if ch == ' ': 
-                if index == 0: 
-                    leading_space = True 
-                if index == len(scalar)-1: 
-                    trailing_space = True 
-                if previous_break: 
-                    break_space = True 
-                previous_space = True 
-                previous_break = False 
-            elif ch in '\n\x85\u2028\u2029': 
-                if index == 0: 
-                    leading_break = True 
-                if index == len(scalar)-1: 
-                    trailing_break = True 
-                if previous_space: 
-                    space_break = True 
-                previous_space = False 
-                previous_break = True 
-            else: 
-                previous_space = False 
-                previous_break = False 
- 
-            # Prepare for the next character. 
-            index += 1 
+                    unicode_characters = True
+                    if not self.allow_unicode:
+                        special_characters = True
+                else:
+                    special_characters = True
+
+            # Detect important whitespace combinations.
+            if ch == ' ':
+                if index == 0:
+                    leading_space = True
+                if index == len(scalar)-1:
+                    trailing_space = True
+                if previous_break:
+                    break_space = True
+                previous_space = True
+                previous_break = False
+            elif ch in '\n\x85\u2028\u2029':
+                if index == 0:
+                    leading_break = True
+                if index == len(scalar)-1:
+                    trailing_break = True
+                if previous_space:
+                    space_break = True
+                previous_space = False
+                previous_break = True
+            else:
+                previous_space = False
+                previous_break = False
+
+            # Prepare for the next character.
+            index += 1
             preceded_by_whitespace = (ch in '\0 \t\r\n\x85\u2028\u2029')
-            followed_by_whitespace = (index+1 >= len(scalar) or 
-                    scalar[index+1] in '\0 \t\r\n\x85\u2028\u2029') 
- 
-        # Let's decide what styles are allowed. 
-        allow_flow_plain = True 
-        allow_block_plain = True 
-        allow_single_quoted = True 
-        allow_double_quoted = True 
-        allow_block = True 
- 
-        # Leading and trailing whitespaces are bad for plain scalars. 
-        if (leading_space or leading_break 
-                or trailing_space or trailing_break): 
-            allow_flow_plain = allow_block_plain = False 
- 
-        # We do not permit trailing spaces for block scalars. 
-        if trailing_space: 
-            allow_block = False 
- 
-        # Spaces at the beginning of a new line are only acceptable for block 
-        # scalars. 
-        if break_space: 
-            allow_flow_plain = allow_block_plain = allow_single_quoted = False 
- 
-        # Spaces followed by breaks, as well as special character are only 
-        # allowed for double quoted scalars. 
-        if space_break or special_characters: 
-            allow_flow_plain = allow_block_plain =  \ 
-            allow_single_quoted = allow_block = False 
- 
-        # Although the plain scalar writer supports breaks, we never emit 
-        # multiline plain scalars. 
-        if line_breaks: 
-            allow_flow_plain = allow_block_plain = False 
- 
-        # Flow indicators are forbidden for flow plain scalars. 
-        if flow_indicators: 
-            allow_flow_plain = False 
- 
-        # Block indicators are forbidden for block plain scalars. 
-        if block_indicators: 
-            allow_block_plain = False 
- 
-        return ScalarAnalysis(scalar=scalar, 
-                empty=False, multiline=line_breaks, 
-                allow_flow_plain=allow_flow_plain, 
-                allow_block_plain=allow_block_plain, 
-                allow_single_quoted=allow_single_quoted, 
-                allow_double_quoted=allow_double_quoted, 
-                allow_block=allow_block) 
- 
-    # Writers. 
- 
-    def flush_stream(self): 
-        if hasattr(self.stream, 'flush'): 
-            self.stream.flush() 
- 
-    def write_stream_start(self): 
-        # Write BOM if needed. 
-        if self.encoding and self.encoding.startswith('utf-16'): 
-            self.stream.write('\uFEFF'.encode(self.encoding)) 
- 
-    def write_stream_end(self): 
-        self.flush_stream() 
- 
-    def write_indicator(self, indicator, need_whitespace, 
-            whitespace=False, indention=False): 
-        if self.whitespace or not need_whitespace: 
-            data = indicator 
-        else: 
-            data = ' '+indicator 
-        self.whitespace = whitespace 
-        self.indention = self.indention and indention 
-        self.column += len(data) 
-        self.open_ended = False 
-        if self.encoding: 
-            data = data.encode(self.encoding) 
-        self.stream.write(data) 
- 
-    def write_indent(self): 
-        indent = self.indent or 0 
-        if not self.indention or self.column > indent   \ 
-                or (self.column == indent and not self.whitespace): 
-            self.write_line_break() 
-        if self.column < indent: 
-            self.whitespace = True 
-            data = ' '*(indent-self.column) 
-            self.column = indent 
-            if self.encoding: 
-                data = data.encode(self.encoding) 
-            self.stream.write(data) 
- 
-    def write_line_break(self, data=None): 
-        if data is None: 
-            data = self.best_line_break 
-        self.whitespace = True 
-        self.indention = True 
-        self.line += 1 
-        self.column = 0 
-        if self.encoding: 
-            data = data.encode(self.encoding) 
-        self.stream.write(data) 
- 
-    def write_version_directive(self, version_text): 
-        data = '%%YAML %s' % version_text 
-        if self.encoding: 
-            data = data.encode(self.encoding) 
-        self.stream.write(data) 
-        self.write_line_break() 
- 
-    def write_tag_directive(self, handle_text, prefix_text): 
-        data = '%%TAG %s %s' % (handle_text, prefix_text) 
-        if self.encoding: 
-            data = data.encode(self.encoding) 
-        self.stream.write(data) 
-        self.write_line_break() 
- 
-    # Scalar streams. 
- 
-    def write_single_quoted(self, text, split=True): 
-        self.write_indicator('\'', True) 
-        spaces = False 
-        breaks = False 
-        start = end = 0 
-        while end <= len(text): 
-            ch = None 
-            if end < len(text): 
-                ch = text[end] 
-            if spaces: 
-                if ch is None or ch != ' ': 
-                    if start+1 == end and self.column > self.best_width and split   \ 
-                            and start != 0 and end != len(text): 
-                        self.write_indent() 
-                    else: 
-                        data = text[start:end] 
-                        self.column += len(data) 
-                        if self.encoding: 
-                            data = data.encode(self.encoding) 
-                        self.stream.write(data) 
-                    start = end 
-            elif breaks: 
-                if ch is None or ch not in '\n\x85\u2028\u2029': 
-                    if text[start] == '\n': 
-                        self.write_line_break() 
-                    for br in text[start:end]: 
-                        if br == '\n': 
-                            self.write_line_break() 
-                        else: 
-                            self.write_line_break(br) 
-                    self.write_indent() 
-                    start = end 
-            else: 
-                if ch is None or ch in ' \n\x85\u2028\u2029' or ch == '\'': 
-                    if start < end: 
-                        data = text[start:end] 
-                        self.column += len(data) 
-                        if self.encoding: 
-                            data = data.encode(self.encoding) 
-                        self.stream.write(data) 
-                        start = end 
-            if ch == '\'': 
-                data = '\'\'' 
-                self.column += 2 
-                if self.encoding: 
-                    data = data.encode(self.encoding) 
-                self.stream.write(data) 
-                start = end + 1 
-            if ch is not None: 
-                spaces = (ch == ' ') 
-                breaks = (ch in '\n\x85\u2028\u2029') 
-            end += 1 
-        self.write_indicator('\'', False) 
- 
-    ESCAPE_REPLACEMENTS = { 
-        '\0':       '0', 
-        '\x07':     'a', 
-        '\x08':     'b', 
-        '\x09':     't', 
-        '\x0A':     'n', 
-        '\x0B':     'v', 
-        '\x0C':     'f', 
-        '\x0D':     'r', 
-        '\x1B':     'e', 
-        '\"':       '\"', 
-        '\\':       '\\', 
-        '\x85':     'N', 
-        '\xA0':     '_', 
-        '\u2028':   'L', 
-        '\u2029':   'P', 
-    } 
- 
-    def write_double_quoted(self, text, split=True): 
-        self.write_indicator('"', True) 
-        start = end = 0 
-        while end <= len(text): 
-            ch = None 
-            if end < len(text): 
-                ch = text[end] 
-            if ch is None or ch in '"\\\x85\u2028\u2029\uFEFF' \ 
-                    or not ('\x20' <= ch <= '\x7E' 
-                        or (self.allow_unicode 
-                            and ('\xA0' <= ch <= '\uD7FF' 
-                                or '\uE000' <= ch <= '\uFFFD'))): 
-                if start < end: 
-                    data = text[start:end] 
-                    self.column += len(data) 
-                    if self.encoding: 
-                        data = data.encode(self.encoding) 
-                    self.stream.write(data) 
-                    start = end 
-                if ch is not None: 
-                    if ch in self.ESCAPE_REPLACEMENTS: 
-                        data = '\\'+self.ESCAPE_REPLACEMENTS[ch] 
-                    elif ch <= '\xFF': 
-                        data = '\\x%02X' % ord(ch) 
-                    elif ch <= '\uFFFF': 
-                        data = '\\u%04X' % ord(ch) 
-                    else: 
-                        data = '\\U%08X' % ord(ch) 
-                    self.column += len(data) 
-                    if self.encoding: 
-                        data = data.encode(self.encoding) 
-                    self.stream.write(data) 
-                    start = end+1 
-            if 0 < end < len(text)-1 and (ch == ' ' or start >= end)    \ 
-                    and self.column+(end-start) > self.best_width and split: 
-                data = text[start:end]+'\\' 
-                if start < end: 
-                    start = end 
-                self.column += len(data) 
-                if self.encoding: 
-                    data = data.encode(self.encoding) 
-                self.stream.write(data) 
-                self.write_indent() 
-                self.whitespace = False 
-                self.indention = False 
-                if text[start] == ' ': 
-                    data = '\\' 
-                    self.column += len(data) 
-                    if self.encoding: 
-                        data = data.encode(self.encoding) 
-                    self.stream.write(data) 
-            end += 1 
-        self.write_indicator('"', False) 
- 
-    def determine_block_hints(self, text): 
-        hints = '' 
-        if text: 
-            if text[0] in ' \n\x85\u2028\u2029': 
-                hints += str(self.best_indent) 
-            if text[-1] not in '\n\x85\u2028\u2029': 
-                hints += '-' 
-            elif len(text) == 1 or text[-2] in '\n\x85\u2028\u2029': 
-                hints += '+' 
-        return hints 
- 
-    def write_folded(self, text): 
-        hints = self.determine_block_hints(text) 
-        self.write_indicator('>'+hints, True) 
-        if hints[-1:] == '+': 
-            self.open_ended = True 
-        self.write_line_break() 
-        leading_space = True 
-        spaces = False 
-        breaks = True 
-        start = end = 0 
-        while end <= len(text): 
-            ch = None 
-            if end < len(text): 
-                ch = text[end] 
-            if breaks: 
-                if ch is None or ch not in '\n\x85\u2028\u2029': 
-                    if not leading_space and ch is not None and ch != ' '   \ 
-                            and text[start] == '\n': 
-                        self.write_line_break() 
-                    leading_space = (ch == ' ') 
-                    for br in text[start:end]: 
-                        if br == '\n': 
-                            self.write_line_break() 
-                        else: 
-                            self.write_line_break(br) 
-                    if ch is not None: 
-                        self.write_indent() 
-                    start = end 
-            elif spaces: 
-                if ch != ' ': 
-                    if start+1 == end and self.column > self.best_width: 
-                        self.write_indent() 
-                    else: 
-                        data = text[start:end] 
-                        self.column += len(data) 
-                        if self.encoding: 
-                            data = data.encode(self.encoding) 
-                        self.stream.write(data) 
-                    start = end 
-            else: 
-                if ch is None or ch in ' \n\x85\u2028\u2029': 
-                    data = text[start:end] 
-                    self.column += len(data) 
-                    if self.encoding: 
-                        data = data.encode(self.encoding) 
-                    self.stream.write(data) 
-                    if ch is None: 
-                        self.write_line_break() 
-                    start = end 
-            if ch is not None: 
-                breaks = (ch in '\n\x85\u2028\u2029') 
-                spaces = (ch == ' ') 
-            end += 1 
- 
-    def write_literal(self, text): 
-        hints = self.determine_block_hints(text) 
-        self.write_indicator('|'+hints, True) 
-        if hints[-1:] == '+': 
-            self.open_ended = True 
-        self.write_line_break() 
-        breaks = True 
-        start = end = 0 
-        while end <= len(text): 
-            ch = None 
-            if end < len(text): 
-                ch = text[end] 
-            if breaks: 
-                if ch is None or ch not in '\n\x85\u2028\u2029': 
-                    for br in text[start:end]: 
-                        if br == '\n': 
-                            self.write_line_break() 
-                        else: 
-                            self.write_line_break(br) 
-                    if ch is not None: 
-                        self.write_indent() 
-                    start = end 
-            else: 
-                if ch is None or ch in '\n\x85\u2028\u2029': 
-                    data = text[start:end] 
-                    if self.encoding: 
-                        data = data.encode(self.encoding) 
-                    self.stream.write(data) 
-                    if ch is None: 
-                        self.write_line_break() 
-                    start = end 
-            if ch is not None: 
-                breaks = (ch in '\n\x85\u2028\u2029') 
-            end += 1 
- 
-    def write_plain(self, text, split=True): 
-        if self.root_context: 
-            self.open_ended = True 
-        if not text: 
-            return 
-        if not self.whitespace: 
-            data = ' ' 
-            self.column += len(data) 
-            if self.encoding: 
-                data = data.encode(self.encoding) 
-            self.stream.write(data) 
-        self.whitespace = False 
-        self.indention = False 
-        spaces = False 
-        breaks = False 
-        start = end = 0 
-        while end <= len(text): 
-            ch = None 
-            if end < len(text): 
-                ch = text[end] 
-            if spaces: 
-                if ch != ' ': 
-                    if start+1 == end and self.column > self.best_width and split: 
-                        self.write_indent() 
-                        self.whitespace = False 
-                        self.indention = False 
-                    else: 
-                        data = text[start:end] 
-                        self.column += len(data) 
-                        if self.encoding: 
-                            data = data.encode(self.encoding) 
-                        self.stream.write(data) 
-                    start = end 
-            elif breaks: 
-                if ch not in '\n\x85\u2028\u2029': 
-                    if text[start] == '\n': 
-                        self.write_line_break() 
-                    for br in text[start:end]: 
-                        if br == '\n': 
-                            self.write_line_break() 
-                        else: 
-                            self.write_line_break(br) 
-                    self.write_indent() 
-                    self.whitespace = False 
-                    self.indention = False 
-                    start = end 
-            else: 
-                if ch is None or ch in ' \n\x85\u2028\u2029': 
-                    data = text[start:end] 
-                    self.column += len(data) 
-                    if self.encoding: 
-                        data = data.encode(self.encoding) 
-                    self.stream.write(data) 
-                    start = end 
-            if ch is not None: 
-                spaces = (ch == ' ') 
-                breaks = (ch in '\n\x85\u2028\u2029') 
-            end += 1 
+            followed_by_whitespace = (index+1 >= len(scalar) or
+                    scalar[index+1] in '\0 \t\r\n\x85\u2028\u2029')
+
+        # Let's decide what styles are allowed.
+        allow_flow_plain = True
+        allow_block_plain = True
+        allow_single_quoted = True
+        allow_double_quoted = True
+        allow_block = True
+
+        # Leading and trailing whitespaces are bad for plain scalars.
+        if (leading_space or leading_break
+                or trailing_space or trailing_break):
+            allow_flow_plain = allow_block_plain = False
+
+        # We do not permit trailing spaces for block scalars.
+        if trailing_space:
+            allow_block = False
+
+        # Spaces at the beginning of a new line are only acceptable for block
+        # scalars.
+        if break_space:
+            allow_flow_plain = allow_block_plain = allow_single_quoted = False
+
+        # Spaces followed by breaks, as well as special character are only
+        # allowed for double quoted scalars.
+        if space_break or special_characters:
+            allow_flow_plain = allow_block_plain =  \
+            allow_single_quoted = allow_block = False
+
+        # Although the plain scalar writer supports breaks, we never emit
+        # multiline plain scalars.
+        if line_breaks:
+            allow_flow_plain = allow_block_plain = False
+
+        # Flow indicators are forbidden for flow plain scalars.
+        if flow_indicators:
+            allow_flow_plain = False
+
+        # Block indicators are forbidden for block plain scalars.
+        if block_indicators:
+            allow_block_plain = False
+
+        return ScalarAnalysis(scalar=scalar,
+                empty=False, multiline=line_breaks,
+                allow_flow_plain=allow_flow_plain,
+                allow_block_plain=allow_block_plain,
+                allow_single_quoted=allow_single_quoted,
+                allow_double_quoted=allow_double_quoted,
+                allow_block=allow_block)
+
+    # Writers.
+
+    def flush_stream(self):
+        if hasattr(self.stream, 'flush'):
+            self.stream.flush()
+
+    def write_stream_start(self):
+        # Write BOM if needed.
+        if self.encoding and self.encoding.startswith('utf-16'):
+            self.stream.write('\uFEFF'.encode(self.encoding))
+
+    def write_stream_end(self):
+        self.flush_stream()
+
+    def write_indicator(self, indicator, need_whitespace,
+            whitespace=False, indention=False):
+        if self.whitespace or not need_whitespace:
+            data = indicator
+        else:
+            data = ' '+indicator
+        self.whitespace = whitespace
+        self.indention = self.indention and indention
+        self.column += len(data)
+        self.open_ended = False
+        if self.encoding:
+            data = data.encode(self.encoding)
+        self.stream.write(data)
+
+    def write_indent(self):
+        indent = self.indent or 0
+        if not self.indention or self.column > indent   \
+                or (self.column == indent and not self.whitespace):
+            self.write_line_break()
+        if self.column < indent:
+            self.whitespace = True
+            data = ' '*(indent-self.column)
+            self.column = indent
+            if self.encoding:
+                data = data.encode(self.encoding)
+            self.stream.write(data)
+
+    def write_line_break(self, data=None):
+        if data is None:
+            data = self.best_line_break
+        self.whitespace = True
+        self.indention = True
+        self.line += 1
+        self.column = 0
+        if self.encoding:
+            data = data.encode(self.encoding)
+        self.stream.write(data)
+
+    def write_version_directive(self, version_text):
+        data = '%%YAML %s' % version_text
+        if self.encoding:
+            data = data.encode(self.encoding)
+        self.stream.write(data)
+        self.write_line_break()
+
+    def write_tag_directive(self, handle_text, prefix_text):
+        data = '%%TAG %s %s' % (handle_text, prefix_text)
+        if self.encoding:
+            data = data.encode(self.encoding)
+        self.stream.write(data)
+        self.write_line_break()
+
+    # Scalar streams.
+
+    def write_single_quoted(self, text, split=True):
+        self.write_indicator('\'', True)
+        spaces = False
+        breaks = False
+        start = end = 0
+        while end <= len(text):
+            ch = None
+            if end < len(text):
+                ch = text[end]
+            if spaces:
+                if ch is None or ch != ' ':
+                    if start+1 == end and self.column > self.best_width and split   \
+                            and start != 0 and end != len(text):
+                        self.write_indent()
+                    else:
+                        data = text[start:end]
+                        self.column += len(data)
+                        if self.encoding:
+                            data = data.encode(self.encoding)
+                        self.stream.write(data)
+                    start = end
+            elif breaks:
+                if ch is None or ch not in '\n\x85\u2028\u2029':
+                    if text[start] == '\n':
+                        self.write_line_break()
+                    for br in text[start:end]:
+                        if br == '\n':
+                            self.write_line_break()
+                        else:
+                            self.write_line_break(br)
+                    self.write_indent()
+                    start = end
+            else:
+                if ch is None or ch in ' \n\x85\u2028\u2029' or ch == '\'':
+                    if start < end:
+                        data = text[start:end]
+                        self.column += len(data)
+                        if self.encoding:
+                            data = data.encode(self.encoding)
+                        self.stream.write(data)
+                        start = end
+            if ch == '\'':
+                data = '\'\''
+                self.column += 2
+                if self.encoding:
+                    data = data.encode(self.encoding)
+                self.stream.write(data)
+                start = end + 1
+            if ch is not None:
+                spaces = (ch == ' ')
+                breaks = (ch in '\n\x85\u2028\u2029')
+            end += 1
+        self.write_indicator('\'', False)
+
+    ESCAPE_REPLACEMENTS = {
+        '\0':       '0',
+        '\x07':     'a',
+        '\x08':     'b',
+        '\x09':     't',
+        '\x0A':     'n',
+        '\x0B':     'v',
+        '\x0C':     'f',
+        '\x0D':     'r',
+        '\x1B':     'e',
+        '\"':       '\"',
+        '\\':       '\\',
+        '\x85':     'N',
+        '\xA0':     '_',
+        '\u2028':   'L',
+        '\u2029':   'P',
+    }
+
+    def write_double_quoted(self, text, split=True):
+        self.write_indicator('"', True)
+        start = end = 0
+        while end <= len(text):
+            ch = None
+            if end < len(text):
+                ch = text[end]
+            if ch is None or ch in '"\\\x85\u2028\u2029\uFEFF' \
+                    or not ('\x20' <= ch <= '\x7E'
+                        or (self.allow_unicode
+                            and ('\xA0' <= ch <= '\uD7FF'
+                                or '\uE000' <= ch <= '\uFFFD'))):
+                if start < end:
+                    data = text[start:end]
+                    self.column += len(data)
+                    if self.encoding:
+                        data = data.encode(self.encoding)
+                    self.stream.write(data)
+                    start = end
+                if ch is not None:
+                    if ch in self.ESCAPE_REPLACEMENTS:
+                        data = '\\'+self.ESCAPE_REPLACEMENTS[ch]
+                    elif ch <= '\xFF':
+                        data = '\\x%02X' % ord(ch)
+                    elif ch <= '\uFFFF':
+                        data = '\\u%04X' % ord(ch)
+                    else:
+                        data = '\\U%08X' % ord(ch)
+                    self.column += len(data)
+                    if self.encoding:
+                        data = data.encode(self.encoding)
+                    self.stream.write(data)
+                    start = end+1
+            if 0 < end < len(text)-1 and (ch == ' ' or start >= end)    \
+                    and self.column+(end-start) > self.best_width and split:
+                data = text[start:end]+'\\'
+                if start < end:
+                    start = end
+                self.column += len(data)
+                if self.encoding:
+                    data = data.encode(self.encoding)
+                self.stream.write(data)
+                self.write_indent()
+                self.whitespace = False
+                self.indention = False
+                if text[start] == ' ':
+                    data = '\\'
+                    self.column += len(data)
+                    if self.encoding:
+                        data = data.encode(self.encoding)
+                    self.stream.write(data)
+            end += 1
+        self.write_indicator('"', False)
+
+    def determine_block_hints(self, text):
+        hints = ''
+        if text:
+            if text[0] in ' \n\x85\u2028\u2029':
+                hints += str(self.best_indent)
+            if text[-1] not in '\n\x85\u2028\u2029':
+                hints += '-'
+            elif len(text) == 1 or text[-2] in '\n\x85\u2028\u2029':
+                hints += '+'
+        return hints
+
+    def write_folded(self, text):
+        hints = self.determine_block_hints(text)
+        self.write_indicator('>'+hints, True)
+        if hints[-1:] == '+':
+            self.open_ended = True
+        self.write_line_break()
+        leading_space = True
+        spaces = False
+        breaks = True
+        start = end = 0
+        while end <= len(text):
+            ch = None
+            if end < len(text):
+                ch = text[end]
+            if breaks:
+                if ch is None or ch not in '\n\x85\u2028\u2029':
+                    if not leading_space and ch is not None and ch != ' '   \
+                            and text[start] == '\n':
+                        self.write_line_break()
+                    leading_space = (ch == ' ')
+                    for br in text[start:end]:
+                        if br == '\n':
+                            self.write_line_break()
+                        else:
+                            self.write_line_break(br)
+                    if ch is not None:
+                        self.write_indent()
+                    start = end
+            elif spaces:
+                if ch != ' ':
+                    if start+1 == end and self.column > self.best_width:
+                        self.write_indent()
+                    else:
+                        data = text[start:end]
+                        self.column += len(data)
+                        if self.encoding:
+                            data = data.encode(self.encoding)
+                        self.stream.write(data)
+                    start = end
+            else:
+                if ch is None or ch in ' \n\x85\u2028\u2029':
+                    data = text[start:end]
+                    self.column += len(data)
+                    if self.encoding:
+                        data = data.encode(self.encoding)
+                    self.stream.write(data)
+                    if ch is None:
+                        self.write_line_break()
+                    start = end
+            if ch is not None:
+                breaks = (ch in '\n\x85\u2028\u2029')
+                spaces = (ch == ' ')
+            end += 1
+
+    def write_literal(self, text):
+        hints = self.determine_block_hints(text)
+        self.write_indicator('|'+hints, True)
+        if hints[-1:] == '+':
+            self.open_ended = True
+        self.write_line_break()
+        breaks = True
+        start = end = 0
+        while end <= len(text):
+            ch = None
+            if end < len(text):
+                ch = text[end]
+            if breaks:
+                if ch is None or ch not in '\n\x85\u2028\u2029':
+                    for br in text[start:end]:
+                        if br == '\n':
+                            self.write_line_break()
+                        else:
+                            self.write_line_break(br)
+                    if ch is not None:
+                        self.write_indent()
+                    start = end
+            else:
+                if ch is None or ch in '\n\x85\u2028\u2029':
+                    data = text[start:end]
+                    if self.encoding:
+                        data = data.encode(self.encoding)
+                    self.stream.write(data)
+                    if ch is None:
+                        self.write_line_break()
+                    start = end
+            if ch is not None:
+                breaks = (ch in '\n\x85\u2028\u2029')
+            end += 1
+
+    def write_plain(self, text, split=True):
+        if self.root_context:
+            self.open_ended = True
+        if not text:
+            return
+        if not self.whitespace:
+            data = ' '
+            self.column += len(data)
+            if self.encoding:
+                data = data.encode(self.encoding)
+            self.stream.write(data)
+        self.whitespace = False
+        self.indention = False
+        spaces = False
+        breaks = False
+        start = end = 0
+        while end <= len(text):
+            ch = None
+            if end < len(text):
+                ch = text[end]
+            if spaces:
+                if ch != ' ':
+                    if start+1 == end and self.column > self.best_width and split:
+                        self.write_indent()
+                        self.whitespace = False
+                        self.indention = False
+                    else:
+                        data = text[start:end]
+                        self.column += len(data)
+                        if self.encoding:
+                            data = data.encode(self.encoding)
+                        self.stream.write(data)
+                    start = end
+            elif breaks:
+                if ch not in '\n\x85\u2028\u2029':
+                    if text[start] == '\n':
+                        self.write_line_break()
+                    for br in text[start:end]:
+                        if br == '\n':
+                            self.write_line_break()
+                        else:
+                            self.write_line_break(br)
+                    self.write_indent()
+                    self.whitespace = False
+                    self.indention = False
+                    start = end
+            else:
+                if ch is None or ch in ' \n\x85\u2028\u2029':
+                    data = text[start:end]
+                    self.column += len(data)
+                    if self.encoding:
+                        data = data.encode(self.encoding)
+                    self.stream.write(data)
+                    start = end
+            if ch is not None:
+                spaces = (ch == ' ')
+                breaks = (ch in '\n\x85\u2028\u2029')
+            end += 1
diff --git a/contrib/python/PyYAML/py3/yaml/error.py b/contrib/python/PyYAML/py3/yaml/error.py
index 0ec669f2b5..b796b4dc51 100644
--- a/contrib/python/PyYAML/py3/yaml/error.py
+++ b/contrib/python/PyYAML/py3/yaml/error.py
@@ -1,75 +1,75 @@
- 
-__all__ = ['Mark', 'YAMLError', 'MarkedYAMLError'] 
- 
-class Mark: 
- 
-    def __init__(self, name, index, line, column, buffer, pointer): 
-        self.name = name 
-        self.index = index 
-        self.line = line 
-        self.column = column 
-        self.buffer = buffer 
-        self.pointer = pointer 
- 
-    def get_snippet(self, indent=4, max_length=75): 
-        if self.buffer is None: 
-            return None 
-        head = '' 
-        start = self.pointer 
-        while start > 0 and self.buffer[start-1] not in '\0\r\n\x85\u2028\u2029': 
-            start -= 1 
-            if self.pointer-start > max_length/2-1: 
-                head = ' ... ' 
-                start += 5 
-                break 
-        tail = '' 
-        end = self.pointer 
-        while end < len(self.buffer) and self.buffer[end] not in '\0\r\n\x85\u2028\u2029': 
-            end += 1 
-            if end-self.pointer > max_length/2-1: 
-                tail = ' ... ' 
-                end -= 5 
-                break 
-        snippet = self.buffer[start:end] 
-        return ' '*indent + head + snippet + tail + '\n'  \ 
-                + ' '*(indent+self.pointer-start+len(head)) + '^' 
- 
-    def __str__(self): 
-        snippet = self.get_snippet() 
-        where = "  in \"%s\", line %d, column %d"   \ 
-                % (self.name, self.line+1, self.column+1) 
-        if snippet is not None: 
-            where += ":\n"+snippet 
-        return where 
- 
-class YAMLError(Exception): 
-    pass 
- 
-class MarkedYAMLError(YAMLError): 
- 
-    def __init__(self, context=None, context_mark=None, 
-            problem=None, problem_mark=None, note=None): 
-        self.context = context 
-        self.context_mark = context_mark 
-        self.problem = problem 
-        self.problem_mark = problem_mark 
-        self.note = note 
- 
-    def __str__(self): 
-        lines = [] 
-        if self.context is not None: 
-            lines.append(self.context) 
-        if self.context_mark is not None  \ 
-            and (self.problem is None or self.problem_mark is None 
-                    or self.context_mark.name != self.problem_mark.name 
-                    or self.context_mark.line != self.problem_mark.line 
-                    or self.context_mark.column != self.problem_mark.column): 
-            lines.append(str(self.context_mark)) 
-        if self.problem is not None: 
-            lines.append(self.problem) 
-        if self.problem_mark is not None: 
-            lines.append(str(self.problem_mark)) 
-        if self.note is not None: 
-            lines.append(self.note) 
-        return '\n'.join(lines) 
- 
+
+__all__ = ['Mark', 'YAMLError', 'MarkedYAMLError']
+
+class Mark:
+
+    def __init__(self, name, index, line, column, buffer, pointer):
+        self.name = name
+        self.index = index
+        self.line = line
+        self.column = column
+        self.buffer = buffer
+        self.pointer = pointer
+
+    def get_snippet(self, indent=4, max_length=75):
+        if self.buffer is None:
+            return None
+        head = ''
+        start = self.pointer
+        while start > 0 and self.buffer[start-1] not in '\0\r\n\x85\u2028\u2029':
+            start -= 1
+            if self.pointer-start > max_length/2-1:
+                head = ' ... '
+                start += 5
+                break
+        tail = ''
+        end = self.pointer
+        while end < len(self.buffer) and self.buffer[end] not in '\0\r\n\x85\u2028\u2029':
+            end += 1
+            if end-self.pointer > max_length/2-1:
+                tail = ' ... '
+                end -= 5
+                break
+        snippet = self.buffer[start:end]
+        return ' '*indent + head + snippet + tail + '\n'  \
+                + ' '*(indent+self.pointer-start+len(head)) + '^'
+
+    def __str__(self):
+        snippet = self.get_snippet()
+        where = "  in \"%s\", line %d, column %d"   \
+                % (self.name, self.line+1, self.column+1)
+        if snippet is not None:
+            where += ":\n"+snippet
+        return where
+
+class YAMLError(Exception):
+    pass
+
+class MarkedYAMLError(YAMLError):
+
+    def __init__(self, context=None, context_mark=None,
+            problem=None, problem_mark=None, note=None):
+        self.context = context
+        self.context_mark = context_mark
+        self.problem = problem
+        self.problem_mark = problem_mark
+        self.note = note
+
+    def __str__(self):
+        lines = []
+        if self.context is not None:
+            lines.append(self.context)
+        if self.context_mark is not None  \
+            and (self.problem is None or self.problem_mark is None
+                    or self.context_mark.name != self.problem_mark.name
+                    or self.context_mark.line != self.problem_mark.line
+                    or self.context_mark.column != self.problem_mark.column):
+            lines.append(str(self.context_mark))
+        if self.problem is not None:
+            lines.append(self.problem)
+        if self.problem_mark is not None:
+            lines.append(str(self.problem_mark))
+        if self.note is not None:
+            lines.append(self.note)
+        return '\n'.join(lines)
+
diff --git a/contrib/python/PyYAML/py3/yaml/events.py b/contrib/python/PyYAML/py3/yaml/events.py
index 6325aedb77..f79ad389cb 100644
--- a/contrib/python/PyYAML/py3/yaml/events.py
+++ b/contrib/python/PyYAML/py3/yaml/events.py
@@ -1,86 +1,86 @@
- 
-# Abstract classes. 
- 
-class Event(object): 
-    def __init__(self, start_mark=None, end_mark=None): 
-        self.start_mark = start_mark 
-        self.end_mark = end_mark 
-    def __repr__(self): 
-        attributes = [key for key in ['anchor', 'tag', 'implicit', 'value'] 
-                if hasattr(self, key)] 
-        arguments = ', '.join(['%s=%r' % (key, getattr(self, key)) 
-                for key in attributes]) 
-        return '%s(%s)' % (self.__class__.__name__, arguments) 
- 
-class NodeEvent(Event): 
-    def __init__(self, anchor, start_mark=None, end_mark=None): 
-        self.anchor = anchor 
-        self.start_mark = start_mark 
-        self.end_mark = end_mark 
- 
-class CollectionStartEvent(NodeEvent): 
-    def __init__(self, anchor, tag, implicit, start_mark=None, end_mark=None, 
-            flow_style=None): 
-        self.anchor = anchor 
-        self.tag = tag 
-        self.implicit = implicit 
-        self.start_mark = start_mark 
-        self.end_mark = end_mark 
-        self.flow_style = flow_style 
- 
-class CollectionEndEvent(Event): 
-    pass 
- 
-# Implementations. 
- 
-class StreamStartEvent(Event): 
-    def __init__(self, start_mark=None, end_mark=None, encoding=None): 
-        self.start_mark = start_mark 
-        self.end_mark = end_mark 
-        self.encoding = encoding 
- 
-class StreamEndEvent(Event): 
-    pass 
- 
-class DocumentStartEvent(Event): 
-    def __init__(self, start_mark=None, end_mark=None, 
-            explicit=None, version=None, tags=None): 
-        self.start_mark = start_mark 
-        self.end_mark = end_mark 
-        self.explicit = explicit 
-        self.version = version 
-        self.tags = tags 
- 
-class DocumentEndEvent(Event): 
-    def __init__(self, start_mark=None, end_mark=None, 
-            explicit=None): 
-        self.start_mark = start_mark 
-        self.end_mark = end_mark 
-        self.explicit = explicit 
- 
-class AliasEvent(NodeEvent): 
-    pass 
- 
-class ScalarEvent(NodeEvent): 
-    def __init__(self, anchor, tag, implicit, value, 
-            start_mark=None, end_mark=None, style=None): 
-        self.anchor = anchor 
-        self.tag = tag 
-        self.implicit = implicit 
-        self.value = value 
-        self.start_mark = start_mark 
-        self.end_mark = end_mark 
-        self.style = style 
- 
-class SequenceStartEvent(CollectionStartEvent): 
-    pass 
- 
-class SequenceEndEvent(CollectionEndEvent): 
-    pass 
- 
-class MappingStartEvent(CollectionStartEvent): 
-    pass 
- 
-class MappingEndEvent(CollectionEndEvent): 
-    pass 
- 
+
+# Abstract classes.
+
+class Event(object):
+    def __init__(self, start_mark=None, end_mark=None):
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+    def __repr__(self):
+        attributes = [key for key in ['anchor', 'tag', 'implicit', 'value']
+                if hasattr(self, key)]
+        arguments = ', '.join(['%s=%r' % (key, getattr(self, key))
+                for key in attributes])
+        return '%s(%s)' % (self.__class__.__name__, arguments)
+
+class NodeEvent(Event):
+    def __init__(self, anchor, start_mark=None, end_mark=None):
+        self.anchor = anchor
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+
+class CollectionStartEvent(NodeEvent):
+    def __init__(self, anchor, tag, implicit, start_mark=None, end_mark=None,
+            flow_style=None):
+        self.anchor = anchor
+        self.tag = tag
+        self.implicit = implicit
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+        self.flow_style = flow_style
+
+class CollectionEndEvent(Event):
+    pass
+
+# Implementations.
+
+class StreamStartEvent(Event):
+    def __init__(self, start_mark=None, end_mark=None, encoding=None):
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+        self.encoding = encoding
+
+class StreamEndEvent(Event):
+    pass
+
+class DocumentStartEvent(Event):
+    def __init__(self, start_mark=None, end_mark=None,
+            explicit=None, version=None, tags=None):
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+        self.explicit = explicit
+        self.version = version
+        self.tags = tags
+
+class DocumentEndEvent(Event):
+    def __init__(self, start_mark=None, end_mark=None,
+            explicit=None):
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+        self.explicit = explicit
+
+class AliasEvent(NodeEvent):
+    pass
+
+class ScalarEvent(NodeEvent):
+    def __init__(self, anchor, tag, implicit, value,
+            start_mark=None, end_mark=None, style=None):
+        self.anchor = anchor
+        self.tag = tag
+        self.implicit = implicit
+        self.value = value
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+        self.style = style
+
+class SequenceStartEvent(CollectionStartEvent):
+    pass
+
+class SequenceEndEvent(CollectionEndEvent):
+    pass
+
+class MappingStartEvent(CollectionStartEvent):
+    pass
+
+class MappingEndEvent(CollectionEndEvent):
+    pass
+
diff --git a/contrib/python/PyYAML/py3/yaml/loader.py b/contrib/python/PyYAML/py3/yaml/loader.py
index bdd9090b56..e90c11224c 100644
--- a/contrib/python/PyYAML/py3/yaml/loader.py
+++ b/contrib/python/PyYAML/py3/yaml/loader.py
@@ -1,23 +1,23 @@
- 
+
 __all__ = ['BaseLoader', 'FullLoader', 'SafeLoader', 'Loader', 'UnsafeLoader']
- 
-from .reader import * 
-from .scanner import * 
-from .parser import * 
-from .composer import * 
-from .constructor import * 
-from .resolver import * 
- 
-class BaseLoader(Reader, Scanner, Parser, Composer, BaseConstructor, BaseResolver): 
- 
-    def __init__(self, stream): 
-        Reader.__init__(self, stream) 
-        Scanner.__init__(self) 
-        Parser.__init__(self) 
-        Composer.__init__(self) 
-        BaseConstructor.__init__(self) 
-        BaseResolver.__init__(self) 
- 
+
+from .reader import *
+from .scanner import *
+from .parser import *
+from .composer import *
+from .constructor import *
+from .resolver import *
+
+class BaseLoader(Reader, Scanner, Parser, Composer, BaseConstructor, BaseResolver):
+
+    def __init__(self, stream):
+        Reader.__init__(self, stream)
+        Scanner.__init__(self)
+        Parser.__init__(self)
+        Composer.__init__(self)
+        BaseConstructor.__init__(self)
+        BaseResolver.__init__(self)
+
 class FullLoader(Reader, Scanner, Parser, Composer, FullConstructor, Resolver):
 
     def __init__(self, stream):
@@ -28,26 +28,26 @@ class FullLoader(Reader, Scanner, Parser, Composer, FullConstructor, Resolver):
         FullConstructor.__init__(self)
         Resolver.__init__(self)
 
-class SafeLoader(Reader, Scanner, Parser, Composer, SafeConstructor, Resolver): 
- 
-    def __init__(self, stream): 
-        Reader.__init__(self, stream) 
-        Scanner.__init__(self) 
-        Parser.__init__(self) 
-        Composer.__init__(self) 
-        SafeConstructor.__init__(self) 
-        Resolver.__init__(self) 
- 
-class Loader(Reader, Scanner, Parser, Composer, Constructor, Resolver): 
- 
-    def __init__(self, stream): 
-        Reader.__init__(self, stream) 
-        Scanner.__init__(self) 
-        Parser.__init__(self) 
-        Composer.__init__(self) 
-        Constructor.__init__(self) 
-        Resolver.__init__(self) 
- 
+class SafeLoader(Reader, Scanner, Parser, Composer, SafeConstructor, Resolver):
+
+    def __init__(self, stream):
+        Reader.__init__(self, stream)
+        Scanner.__init__(self)
+        Parser.__init__(self)
+        Composer.__init__(self)
+        SafeConstructor.__init__(self)
+        Resolver.__init__(self)
+
+class Loader(Reader, Scanner, Parser, Composer, Constructor, Resolver):
+
+    def __init__(self, stream):
+        Reader.__init__(self, stream)
+        Scanner.__init__(self)
+        Parser.__init__(self)
+        Composer.__init__(self)
+        Constructor.__init__(self)
+        Resolver.__init__(self)
+
 # UnsafeLoader is the same as Loader (which is and was always unsafe on
 # untrusted input). Use of either Loader or UnsafeLoader should be rare, since
 # FullLoad should be able to load almost all YAML safely. Loader is left intact
diff --git a/contrib/python/PyYAML/py3/yaml/nodes.py b/contrib/python/PyYAML/py3/yaml/nodes.py
index a7858b88e1..c4f070c41e 100644
--- a/contrib/python/PyYAML/py3/yaml/nodes.py
+++ b/contrib/python/PyYAML/py3/yaml/nodes.py
@@ -1,49 +1,49 @@
- 
-class Node(object): 
-    def __init__(self, tag, value, start_mark, end_mark): 
-        self.tag = tag 
-        self.value = value 
-        self.start_mark = start_mark 
-        self.end_mark = end_mark 
-    def __repr__(self): 
-        value = self.value 
-        #if isinstance(value, list): 
-        #    if len(value) == 0: 
-        #        value = '<empty>' 
-        #    elif len(value) == 1: 
-        #        value = '<1 item>' 
-        #    else: 
-        #        value = '<%d items>' % len(value) 
-        #else: 
-        #    if len(value) > 75: 
-        #        value = repr(value[:70]+u' ... ') 
-        #    else: 
-        #        value = repr(value) 
-        value = repr(value) 
-        return '%s(tag=%r, value=%s)' % (self.__class__.__name__, self.tag, value) 
- 
-class ScalarNode(Node): 
-    id = 'scalar' 
-    def __init__(self, tag, value, 
-            start_mark=None, end_mark=None, style=None): 
-        self.tag = tag 
-        self.value = value 
-        self.start_mark = start_mark 
-        self.end_mark = end_mark 
-        self.style = style 
- 
-class CollectionNode(Node): 
-    def __init__(self, tag, value, 
-            start_mark=None, end_mark=None, flow_style=None): 
-        self.tag = tag 
-        self.value = value 
-        self.start_mark = start_mark 
-        self.end_mark = end_mark 
-        self.flow_style = flow_style 
- 
-class SequenceNode(CollectionNode): 
-    id = 'sequence' 
- 
-class MappingNode(CollectionNode): 
-    id = 'mapping' 
- 
+
+class Node(object):
+    def __init__(self, tag, value, start_mark, end_mark):
+        self.tag = tag
+        self.value = value
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+    def __repr__(self):
+        value = self.value
+        #if isinstance(value, list):
+        #    if len(value) == 0:
+        #        value = '<empty>'
+        #    elif len(value) == 1:
+        #        value = '<1 item>'
+        #    else:
+        #        value = '<%d items>' % len(value)
+        #else:
+        #    if len(value) > 75:
+        #        value = repr(value[:70]+u' ... ')
+        #    else:
+        #        value = repr(value)
+        value = repr(value)
+        return '%s(tag=%r, value=%s)' % (self.__class__.__name__, self.tag, value)
+
+class ScalarNode(Node):
+    id = 'scalar'
+    def __init__(self, tag, value,
+            start_mark=None, end_mark=None, style=None):
+        self.tag = tag
+        self.value = value
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+        self.style = style
+
+class CollectionNode(Node):
+    def __init__(self, tag, value,
+            start_mark=None, end_mark=None, flow_style=None):
+        self.tag = tag
+        self.value = value
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+        self.flow_style = flow_style
+
+class SequenceNode(CollectionNode):
+    id = 'sequence'
+
+class MappingNode(CollectionNode):
+    id = 'mapping'
+
diff --git a/contrib/python/PyYAML/py3/yaml/parser.py b/contrib/python/PyYAML/py3/yaml/parser.py
index ff2791f3bf..13a5995d29 100644
--- a/contrib/python/PyYAML/py3/yaml/parser.py
+++ b/contrib/python/PyYAML/py3/yaml/parser.py
@@ -1,589 +1,589 @@
- 
-# The following YAML grammar is LL(1) and is parsed by a recursive descent 
-# parser. 
-# 
-# stream            ::= STREAM-START implicit_document? explicit_document* STREAM-END 
-# implicit_document ::= block_node DOCUMENT-END* 
-# explicit_document ::= DIRECTIVE* DOCUMENT-START block_node? DOCUMENT-END* 
-# block_node_or_indentless_sequence ::= 
-#                       ALIAS 
-#                       | properties (block_content | indentless_block_sequence)? 
-#                       | block_content 
-#                       | indentless_block_sequence 
-# block_node        ::= ALIAS 
-#                       | properties block_content? 
-#                       | block_content 
-# flow_node         ::= ALIAS 
-#                       | properties flow_content? 
-#                       | flow_content 
-# properties        ::= TAG ANCHOR? | ANCHOR TAG? 
-# block_content     ::= block_collection | flow_collection | SCALAR 
-# flow_content      ::= flow_collection | SCALAR 
-# block_collection  ::= block_sequence | block_mapping 
-# flow_collection   ::= flow_sequence | flow_mapping 
-# block_sequence    ::= BLOCK-SEQUENCE-START (BLOCK-ENTRY block_node?)* BLOCK-END 
-# indentless_sequence   ::= (BLOCK-ENTRY block_node?)+ 
-# block_mapping     ::= BLOCK-MAPPING_START 
-#                       ((KEY block_node_or_indentless_sequence?)? 
-#                       (VALUE block_node_or_indentless_sequence?)?)* 
-#                       BLOCK-END 
-# flow_sequence     ::= FLOW-SEQUENCE-START 
-#                       (flow_sequence_entry FLOW-ENTRY)* 
-#                       flow_sequence_entry? 
-#                       FLOW-SEQUENCE-END 
-# flow_sequence_entry   ::= flow_node | KEY flow_node? (VALUE flow_node?)? 
-# flow_mapping      ::= FLOW-MAPPING-START 
-#                       (flow_mapping_entry FLOW-ENTRY)* 
-#                       flow_mapping_entry? 
-#                       FLOW-MAPPING-END 
-# flow_mapping_entry    ::= flow_node | KEY flow_node? (VALUE flow_node?)? 
-# 
-# FIRST sets: 
-# 
-# stream: { STREAM-START } 
-# explicit_document: { DIRECTIVE DOCUMENT-START } 
-# implicit_document: FIRST(block_node) 
-# block_node: { ALIAS TAG ANCHOR SCALAR BLOCK-SEQUENCE-START BLOCK-MAPPING-START FLOW-SEQUENCE-START FLOW-MAPPING-START } 
-# flow_node: { ALIAS ANCHOR TAG SCALAR FLOW-SEQUENCE-START FLOW-MAPPING-START } 
-# block_content: { BLOCK-SEQUENCE-START BLOCK-MAPPING-START FLOW-SEQUENCE-START FLOW-MAPPING-START SCALAR } 
-# flow_content: { FLOW-SEQUENCE-START FLOW-MAPPING-START SCALAR } 
-# block_collection: { BLOCK-SEQUENCE-START BLOCK-MAPPING-START } 
-# flow_collection: { FLOW-SEQUENCE-START FLOW-MAPPING-START } 
-# block_sequence: { BLOCK-SEQUENCE-START } 
-# block_mapping: { BLOCK-MAPPING-START } 
-# block_node_or_indentless_sequence: { ALIAS ANCHOR TAG SCALAR BLOCK-SEQUENCE-START BLOCK-MAPPING-START FLOW-SEQUENCE-START FLOW-MAPPING-START BLOCK-ENTRY } 
-# indentless_sequence: { ENTRY } 
-# flow_collection: { FLOW-SEQUENCE-START FLOW-MAPPING-START } 
-# flow_sequence: { FLOW-SEQUENCE-START } 
-# flow_mapping: { FLOW-MAPPING-START } 
-# flow_sequence_entry: { ALIAS ANCHOR TAG SCALAR FLOW-SEQUENCE-START FLOW-MAPPING-START KEY } 
-# flow_mapping_entry: { ALIAS ANCHOR TAG SCALAR FLOW-SEQUENCE-START FLOW-MAPPING-START KEY } 
- 
-__all__ = ['Parser', 'ParserError'] 
- 
-from .error import MarkedYAMLError 
-from .tokens import * 
-from .events import * 
-from .scanner import * 
- 
-class ParserError(MarkedYAMLError): 
-    pass 
- 
-class Parser: 
-    # Since writing a recursive-descendant parser is a straightforward task, we 
-    # do not give many comments here. 
- 
-    DEFAULT_TAGS = { 
-        '!':   '!', 
-        '!!':  'tag:yaml.org,2002:', 
-    } 
- 
-    def __init__(self): 
-        self.current_event = None 
-        self.yaml_version = None 
-        self.tag_handles = {} 
-        self.states = [] 
-        self.marks = [] 
-        self.state = self.parse_stream_start 
- 
-    def dispose(self): 
-        # Reset the state attributes (to clear self-references) 
-        self.states = [] 
-        self.state = None 
- 
-    def check_event(self, *choices): 
-        # Check the type of the next event. 
-        if self.current_event is None: 
-            if self.state: 
-                self.current_event = self.state() 
-        if self.current_event is not None: 
-            if not choices: 
-                return True 
-            for choice in choices: 
-                if isinstance(self.current_event, choice): 
-                    return True 
-        return False 
- 
-    def peek_event(self): 
-        # Get the next event. 
-        if self.current_event is None: 
-            if self.state: 
-                self.current_event = self.state() 
-        return self.current_event 
- 
-    def get_event(self): 
-        # Get the next event and proceed further. 
-        if self.current_event is None: 
-            if self.state: 
-                self.current_event = self.state() 
-        value = self.current_event 
-        self.current_event = None 
-        return value 
- 
-    # stream    ::= STREAM-START implicit_document? explicit_document* STREAM-END 
-    # implicit_document ::= block_node DOCUMENT-END* 
-    # explicit_document ::= DIRECTIVE* DOCUMENT-START block_node? DOCUMENT-END* 
- 
-    def parse_stream_start(self): 
- 
-        # Parse the stream start. 
-        token = self.get_token() 
-        event = StreamStartEvent(token.start_mark, token.end_mark, 
-                encoding=token.encoding) 
- 
-        # Prepare the next state. 
-        self.state = self.parse_implicit_document_start 
- 
-        return event 
- 
-    def parse_implicit_document_start(self): 
- 
-        # Parse an implicit document. 
-        if not self.check_token(DirectiveToken, DocumentStartToken, 
-                StreamEndToken): 
-            self.tag_handles = self.DEFAULT_TAGS 
-            token = self.peek_token() 
-            start_mark = end_mark = token.start_mark 
-            event = DocumentStartEvent(start_mark, end_mark, 
-                    explicit=False) 
- 
-            # Prepare the next state. 
-            self.states.append(self.parse_document_end) 
-            self.state = self.parse_block_node 
- 
-            return event 
- 
-        else: 
-            return self.parse_document_start() 
- 
-    def parse_document_start(self): 
- 
-        # Parse any extra document end indicators. 
-        while self.check_token(DocumentEndToken): 
-            self.get_token() 
- 
-        # Parse an explicit document. 
-        if not self.check_token(StreamEndToken): 
-            token = self.peek_token() 
-            start_mark = token.start_mark 
-            version, tags = self.process_directives() 
-            if not self.check_token(DocumentStartToken): 
-                raise ParserError(None, None, 
-                        "expected '<document start>', but found %r" 
-                        % self.peek_token().id, 
-                        self.peek_token().start_mark) 
-            token = self.get_token() 
-            end_mark = token.end_mark 
-            event = DocumentStartEvent(start_mark, end_mark, 
-                    explicit=True, version=version, tags=tags) 
-            self.states.append(self.parse_document_end) 
-            self.state = self.parse_document_content 
-        else: 
-            # Parse the end of the stream. 
-            token = self.get_token() 
-            event = StreamEndEvent(token.start_mark, token.end_mark) 
-            assert not self.states 
-            assert not self.marks 
-            self.state = None 
-        return event 
- 
-    def parse_document_end(self): 
- 
-        # Parse the document end. 
-        token = self.peek_token() 
-        start_mark = end_mark = token.start_mark 
-        explicit = False 
-        if self.check_token(DocumentEndToken): 
-            token = self.get_token() 
-            end_mark = token.end_mark 
-            explicit = True 
-        event = DocumentEndEvent(start_mark, end_mark, 
-                explicit=explicit) 
- 
-        # Prepare the next state. 
-        self.state = self.parse_document_start 
- 
-        return event 
- 
-    def parse_document_content(self): 
-        if self.check_token(DirectiveToken, 
-                DocumentStartToken, DocumentEndToken, StreamEndToken): 
-            event = self.process_empty_scalar(self.peek_token().start_mark) 
-            self.state = self.states.pop() 
-            return event 
-        else: 
-            return self.parse_block_node() 
- 
-    def process_directives(self): 
-        self.yaml_version = None 
-        self.tag_handles = {} 
-        while self.check_token(DirectiveToken): 
-            token = self.get_token() 
-            if token.name == 'YAML': 
-                if self.yaml_version is not None: 
-                    raise ParserError(None, None, 
-                            "found duplicate YAML directive", token.start_mark) 
-                major, minor = token.value 
-                if major != 1: 
-                    raise ParserError(None, None, 
-                            "found incompatible YAML document (version 1.* is required)", 
-                            token.start_mark) 
-                self.yaml_version = token.value 
-            elif token.name == 'TAG': 
-                handle, prefix = token.value 
-                if handle in self.tag_handles: 
-                    raise ParserError(None, None, 
-                            "duplicate tag handle %r" % handle, 
-                            token.start_mark) 
-                self.tag_handles[handle] = prefix 
-        if self.tag_handles: 
-            value = self.yaml_version, self.tag_handles.copy() 
-        else: 
-            value = self.yaml_version, None 
-        for key in self.DEFAULT_TAGS: 
-            if key not in self.tag_handles: 
-                self.tag_handles[key] = self.DEFAULT_TAGS[key] 
-        return value 
- 
-    # block_node_or_indentless_sequence ::= ALIAS 
-    #               | properties (block_content | indentless_block_sequence)? 
-    #               | block_content 
-    #               | indentless_block_sequence 
-    # block_node    ::= ALIAS 
-    #                   | properties block_content? 
-    #                   | block_content 
-    # flow_node     ::= ALIAS 
-    #                   | properties flow_content? 
-    #                   | flow_content 
-    # properties    ::= TAG ANCHOR? | ANCHOR TAG? 
-    # block_content     ::= block_collection | flow_collection | SCALAR 
-    # flow_content      ::= flow_collection | SCALAR 
-    # block_collection  ::= block_sequence | block_mapping 
-    # flow_collection   ::= flow_sequence | flow_mapping 
- 
-    def parse_block_node(self): 
-        return self.parse_node(block=True) 
- 
-    def parse_flow_node(self): 
-        return self.parse_node() 
- 
-    def parse_block_node_or_indentless_sequence(self): 
-        return self.parse_node(block=True, indentless_sequence=True) 
- 
-    def parse_node(self, block=False, indentless_sequence=False): 
-        if self.check_token(AliasToken): 
-            token = self.get_token() 
-            event = AliasEvent(token.value, token.start_mark, token.end_mark) 
-            self.state = self.states.pop() 
-        else: 
-            anchor = None 
-            tag = None 
-            start_mark = end_mark = tag_mark = None 
-            if self.check_token(AnchorToken): 
-                token = self.get_token() 
-                start_mark = token.start_mark 
-                end_mark = token.end_mark 
-                anchor = token.value 
-                if self.check_token(TagToken): 
-                    token = self.get_token() 
-                    tag_mark = token.start_mark 
-                    end_mark = token.end_mark 
-                    tag = token.value 
-            elif self.check_token(TagToken): 
-                token = self.get_token() 
-                start_mark = tag_mark = token.start_mark 
-                end_mark = token.end_mark 
-                tag = token.value 
-                if self.check_token(AnchorToken): 
-                    token = self.get_token() 
-                    end_mark = token.end_mark 
-                    anchor = token.value 
-            if tag is not None: 
-                handle, suffix = tag 
-                if handle is not None: 
-                    if handle not in self.tag_handles: 
-                        raise ParserError("while parsing a node", start_mark, 
-                                "found undefined tag handle %r" % handle, 
-                                tag_mark) 
-                    tag = self.tag_handles[handle]+suffix 
-                else: 
-                    tag = suffix 
-            #if tag == '!': 
-            #    raise ParserError("while parsing a node", start_mark, 
-            #            "found non-specific tag '!'", tag_mark, 
-            #            "Please check 'http://pyyaml.org/wiki/YAMLNonSpecificTag' and share your opinion.") 
-            if start_mark is None: 
-                start_mark = end_mark = self.peek_token().start_mark 
-            event = None 
-            implicit = (tag is None or tag == '!') 
-            if indentless_sequence and self.check_token(BlockEntryToken): 
-                end_mark = self.peek_token().end_mark 
-                event = SequenceStartEvent(anchor, tag, implicit, 
-                        start_mark, end_mark) 
-                self.state = self.parse_indentless_sequence_entry 
-            else: 
-                if self.check_token(ScalarToken): 
-                    token = self.get_token() 
-                    end_mark = token.end_mark 
-                    if (token.plain and tag is None) or tag == '!': 
-                        implicit = (True, False) 
-                    elif tag is None: 
-                        implicit = (False, True) 
-                    else: 
-                        implicit = (False, False) 
-                    event = ScalarEvent(anchor, tag, implicit, token.value, 
-                            start_mark, end_mark, style=token.style) 
-                    self.state = self.states.pop() 
-                elif self.check_token(FlowSequenceStartToken): 
-                    end_mark = self.peek_token().end_mark 
-                    event = SequenceStartEvent(anchor, tag, implicit, 
-                            start_mark, end_mark, flow_style=True) 
-                    self.state = self.parse_flow_sequence_first_entry 
-                elif self.check_token(FlowMappingStartToken): 
-                    end_mark = self.peek_token().end_mark 
-                    event = MappingStartEvent(anchor, tag, implicit, 
-                            start_mark, end_mark, flow_style=True) 
-                    self.state = self.parse_flow_mapping_first_key 
-                elif block and self.check_token(BlockSequenceStartToken): 
-                    end_mark = self.peek_token().start_mark 
-                    event = SequenceStartEvent(anchor, tag, implicit, 
-                            start_mark, end_mark, flow_style=False) 
-                    self.state = self.parse_block_sequence_first_entry 
-                elif block and self.check_token(BlockMappingStartToken): 
-                    end_mark = self.peek_token().start_mark 
-                    event = MappingStartEvent(anchor, tag, implicit, 
-                            start_mark, end_mark, flow_style=False) 
-                    self.state = self.parse_block_mapping_first_key 
-                elif anchor is not None or tag is not None: 
-                    # Empty scalars are allowed even if a tag or an anchor is 
-                    # specified. 
-                    event = ScalarEvent(anchor, tag, (implicit, False), '', 
-                            start_mark, end_mark) 
-                    self.state = self.states.pop() 
-                else: 
-                    if block: 
-                        node = 'block' 
-                    else: 
-                        node = 'flow' 
-                    token = self.peek_token() 
-                    raise ParserError("while parsing a %s node" % node, start_mark, 
-                            "expected the node content, but found %r" % token.id, 
-                            token.start_mark) 
-        return event 
- 
-    # block_sequence ::= BLOCK-SEQUENCE-START (BLOCK-ENTRY block_node?)* BLOCK-END 
- 
-    def parse_block_sequence_first_entry(self): 
-        token = self.get_token() 
-        self.marks.append(token.start_mark) 
-        return self.parse_block_sequence_entry() 
- 
-    def parse_block_sequence_entry(self): 
-        if self.check_token(BlockEntryToken): 
-            token = self.get_token() 
-            if not self.check_token(BlockEntryToken, BlockEndToken): 
-                self.states.append(self.parse_block_sequence_entry) 
-                return self.parse_block_node() 
-            else: 
-                self.state = self.parse_block_sequence_entry 
-                return self.process_empty_scalar(token.end_mark) 
-        if not self.check_token(BlockEndToken): 
-            token = self.peek_token() 
-            raise ParserError("while parsing a block collection", self.marks[-1], 
-                    "expected <block end>, but found %r" % token.id, token.start_mark) 
-        token = self.get_token() 
-        event = SequenceEndEvent(token.start_mark, token.end_mark) 
-        self.state = self.states.pop() 
-        self.marks.pop() 
-        return event 
- 
-    # indentless_sequence ::= (BLOCK-ENTRY block_node?)+ 
- 
-    def parse_indentless_sequence_entry(self): 
-        if self.check_token(BlockEntryToken): 
-            token = self.get_token() 
-            if not self.check_token(BlockEntryToken, 
-                    KeyToken, ValueToken, BlockEndToken): 
-                self.states.append(self.parse_indentless_sequence_entry) 
-                return self.parse_block_node() 
-            else: 
-                self.state = self.parse_indentless_sequence_entry 
-                return self.process_empty_scalar(token.end_mark) 
-        token = self.peek_token() 
-        event = SequenceEndEvent(token.start_mark, token.start_mark) 
-        self.state = self.states.pop() 
-        return event 
- 
-    # block_mapping     ::= BLOCK-MAPPING_START 
-    #                       ((KEY block_node_or_indentless_sequence?)? 
-    #                       (VALUE block_node_or_indentless_sequence?)?)* 
-    #                       BLOCK-END 
- 
-    def parse_block_mapping_first_key(self): 
-        token = self.get_token() 
-        self.marks.append(token.start_mark) 
-        return self.parse_block_mapping_key() 
- 
-    def parse_block_mapping_key(self): 
-        if self.check_token(KeyToken): 
-            token = self.get_token() 
-            if not self.check_token(KeyToken, ValueToken, BlockEndToken): 
-                self.states.append(self.parse_block_mapping_value) 
-                return self.parse_block_node_or_indentless_sequence() 
-            else: 
-                self.state = self.parse_block_mapping_value 
-                return self.process_empty_scalar(token.end_mark) 
-        if not self.check_token(BlockEndToken): 
-            token = self.peek_token() 
-            raise ParserError("while parsing a block mapping", self.marks[-1], 
-                    "expected <block end>, but found %r" % token.id, token.start_mark) 
-        token = self.get_token() 
-        event = MappingEndEvent(token.start_mark, token.end_mark) 
-        self.state = self.states.pop() 
-        self.marks.pop() 
-        return event 
- 
-    def parse_block_mapping_value(self): 
-        if self.check_token(ValueToken): 
-            token = self.get_token() 
-            if not self.check_token(KeyToken, ValueToken, BlockEndToken): 
-                self.states.append(self.parse_block_mapping_key) 
-                return self.parse_block_node_or_indentless_sequence() 
-            else: 
-                self.state = self.parse_block_mapping_key 
-                return self.process_empty_scalar(token.end_mark) 
-        else: 
-            self.state = self.parse_block_mapping_key 
-            token = self.peek_token() 
-            return self.process_empty_scalar(token.start_mark) 
- 
-    # flow_sequence     ::= FLOW-SEQUENCE-START 
-    #                       (flow_sequence_entry FLOW-ENTRY)* 
-    #                       flow_sequence_entry? 
-    #                       FLOW-SEQUENCE-END 
-    # flow_sequence_entry   ::= flow_node | KEY flow_node? (VALUE flow_node?)? 
-    # 
-    # Note that while production rules for both flow_sequence_entry and 
-    # flow_mapping_entry are equal, their interpretations are different. 
-    # For `flow_sequence_entry`, the part `KEY flow_node? (VALUE flow_node?)?` 
-    # generate an inline mapping (set syntax). 
- 
-    def parse_flow_sequence_first_entry(self): 
-        token = self.get_token() 
-        self.marks.append(token.start_mark) 
-        return self.parse_flow_sequence_entry(first=True) 
- 
-    def parse_flow_sequence_entry(self, first=False): 
-        if not self.check_token(FlowSequenceEndToken): 
-            if not first: 
-                if self.check_token(FlowEntryToken): 
-                    self.get_token() 
-                else: 
-                    token = self.peek_token() 
-                    raise ParserError("while parsing a flow sequence", self.marks[-1], 
-                            "expected ',' or ']', but got %r" % token.id, token.start_mark) 
-             
-            if self.check_token(KeyToken): 
-                token = self.peek_token() 
-                event = MappingStartEvent(None, None, True, 
-                        token.start_mark, token.end_mark, 
-                        flow_style=True) 
-                self.state = self.parse_flow_sequence_entry_mapping_key 
-                return event 
-            elif not self.check_token(FlowSequenceEndToken): 
-                self.states.append(self.parse_flow_sequence_entry) 
-                return self.parse_flow_node() 
-        token = self.get_token() 
-        event = SequenceEndEvent(token.start_mark, token.end_mark) 
-        self.state = self.states.pop() 
-        self.marks.pop() 
-        return event 
- 
-    def parse_flow_sequence_entry_mapping_key(self): 
-        token = self.get_token() 
-        if not self.check_token(ValueToken, 
-                FlowEntryToken, FlowSequenceEndToken): 
-            self.states.append(self.parse_flow_sequence_entry_mapping_value) 
-            return self.parse_flow_node() 
-        else: 
-            self.state = self.parse_flow_sequence_entry_mapping_value 
-            return self.process_empty_scalar(token.end_mark) 
- 
-    def parse_flow_sequence_entry_mapping_value(self): 
-        if self.check_token(ValueToken): 
-            token = self.get_token() 
-            if not self.check_token(FlowEntryToken, FlowSequenceEndToken): 
-                self.states.append(self.parse_flow_sequence_entry_mapping_end) 
-                return self.parse_flow_node() 
-            else: 
-                self.state = self.parse_flow_sequence_entry_mapping_end 
-                return self.process_empty_scalar(token.end_mark) 
-        else: 
-            self.state = self.parse_flow_sequence_entry_mapping_end 
-            token = self.peek_token() 
-            return self.process_empty_scalar(token.start_mark) 
- 
-    def parse_flow_sequence_entry_mapping_end(self): 
-        self.state = self.parse_flow_sequence_entry 
-        token = self.peek_token() 
-        return MappingEndEvent(token.start_mark, token.start_mark) 
- 
-    # flow_mapping  ::= FLOW-MAPPING-START 
-    #                   (flow_mapping_entry FLOW-ENTRY)* 
-    #                   flow_mapping_entry? 
-    #                   FLOW-MAPPING-END 
-    # flow_mapping_entry    ::= flow_node | KEY flow_node? (VALUE flow_node?)? 
- 
-    def parse_flow_mapping_first_key(self): 
-        token = self.get_token() 
-        self.marks.append(token.start_mark) 
-        return self.parse_flow_mapping_key(first=True) 
- 
-    def parse_flow_mapping_key(self, first=False): 
-        if not self.check_token(FlowMappingEndToken): 
-            if not first: 
-                if self.check_token(FlowEntryToken): 
-                    self.get_token() 
-                else: 
-                    token = self.peek_token() 
-                    raise ParserError("while parsing a flow mapping", self.marks[-1], 
-                            "expected ',' or '}', but got %r" % token.id, token.start_mark) 
-            if self.check_token(KeyToken): 
-                token = self.get_token() 
-                if not self.check_token(ValueToken, 
-                        FlowEntryToken, FlowMappingEndToken): 
-                    self.states.append(self.parse_flow_mapping_value) 
-                    return self.parse_flow_node() 
-                else: 
-                    self.state = self.parse_flow_mapping_value 
-                    return self.process_empty_scalar(token.end_mark) 
-            elif not self.check_token(FlowMappingEndToken): 
-                self.states.append(self.parse_flow_mapping_empty_value) 
-                return self.parse_flow_node() 
-        token = self.get_token() 
-        event = MappingEndEvent(token.start_mark, token.end_mark) 
-        self.state = self.states.pop() 
-        self.marks.pop() 
-        return event 
- 
-    def parse_flow_mapping_value(self): 
-        if self.check_token(ValueToken): 
-            token = self.get_token() 
-            if not self.check_token(FlowEntryToken, FlowMappingEndToken): 
-                self.states.append(self.parse_flow_mapping_key) 
-                return self.parse_flow_node() 
-            else: 
-                self.state = self.parse_flow_mapping_key 
-                return self.process_empty_scalar(token.end_mark) 
-        else: 
-            self.state = self.parse_flow_mapping_key 
-            token = self.peek_token() 
-            return self.process_empty_scalar(token.start_mark) 
- 
-    def parse_flow_mapping_empty_value(self): 
-        self.state = self.parse_flow_mapping_key 
-        return self.process_empty_scalar(self.peek_token().start_mark) 
- 
-    def process_empty_scalar(self, mark): 
-        return ScalarEvent(None, None, (True, False), '', mark, mark) 
- 
+
+# The following YAML grammar is LL(1) and is parsed by a recursive descent
+# parser.
+#
+# stream            ::= STREAM-START implicit_document? explicit_document* STREAM-END
+# implicit_document ::= block_node DOCUMENT-END*
+# explicit_document ::= DIRECTIVE* DOCUMENT-START block_node? DOCUMENT-END*
+# block_node_or_indentless_sequence ::=
+#                       ALIAS
+#                       | properties (block_content | indentless_block_sequence)?
+#                       | block_content
+#                       | indentless_block_sequence
+# block_node        ::= ALIAS
+#                       | properties block_content?
+#                       | block_content
+# flow_node         ::= ALIAS
+#                       | properties flow_content?
+#                       | flow_content
+# properties        ::= TAG ANCHOR? | ANCHOR TAG?
+# block_content     ::= block_collection | flow_collection | SCALAR
+# flow_content      ::= flow_collection | SCALAR
+# block_collection  ::= block_sequence | block_mapping
+# flow_collection   ::= flow_sequence | flow_mapping
+# block_sequence    ::= BLOCK-SEQUENCE-START (BLOCK-ENTRY block_node?)* BLOCK-END
+# indentless_sequence   ::= (BLOCK-ENTRY block_node?)+
+# block_mapping     ::= BLOCK-MAPPING_START
+#                       ((KEY block_node_or_indentless_sequence?)?
+#                       (VALUE block_node_or_indentless_sequence?)?)*
+#                       BLOCK-END
+# flow_sequence     ::= FLOW-SEQUENCE-START
+#                       (flow_sequence_entry FLOW-ENTRY)*
+#                       flow_sequence_entry?
+#                       FLOW-SEQUENCE-END
+# flow_sequence_entry   ::= flow_node | KEY flow_node? (VALUE flow_node?)?
+# flow_mapping      ::= FLOW-MAPPING-START
+#                       (flow_mapping_entry FLOW-ENTRY)*
+#                       flow_mapping_entry?
+#                       FLOW-MAPPING-END
+# flow_mapping_entry    ::= flow_node | KEY flow_node? (VALUE flow_node?)?
+#
+# FIRST sets:
+#
+# stream: { STREAM-START }
+# explicit_document: { DIRECTIVE DOCUMENT-START }
+# implicit_document: FIRST(block_node)
+# block_node: { ALIAS TAG ANCHOR SCALAR BLOCK-SEQUENCE-START BLOCK-MAPPING-START FLOW-SEQUENCE-START FLOW-MAPPING-START }
+# flow_node: { ALIAS ANCHOR TAG SCALAR FLOW-SEQUENCE-START FLOW-MAPPING-START }
+# block_content: { BLOCK-SEQUENCE-START BLOCK-MAPPING-START FLOW-SEQUENCE-START FLOW-MAPPING-START SCALAR }
+# flow_content: { FLOW-SEQUENCE-START FLOW-MAPPING-START SCALAR }
+# block_collection: { BLOCK-SEQUENCE-START BLOCK-MAPPING-START }
+# flow_collection: { FLOW-SEQUENCE-START FLOW-MAPPING-START }
+# block_sequence: { BLOCK-SEQUENCE-START }
+# block_mapping: { BLOCK-MAPPING-START }
+# block_node_or_indentless_sequence: { ALIAS ANCHOR TAG SCALAR BLOCK-SEQUENCE-START BLOCK-MAPPING-START FLOW-SEQUENCE-START FLOW-MAPPING-START BLOCK-ENTRY }
+# indentless_sequence: { ENTRY }
+# flow_collection: { FLOW-SEQUENCE-START FLOW-MAPPING-START }
+# flow_sequence: { FLOW-SEQUENCE-START }
+# flow_mapping: { FLOW-MAPPING-START }
+# flow_sequence_entry: { ALIAS ANCHOR TAG SCALAR FLOW-SEQUENCE-START FLOW-MAPPING-START KEY }
+# flow_mapping_entry: { ALIAS ANCHOR TAG SCALAR FLOW-SEQUENCE-START FLOW-MAPPING-START KEY }
+
+__all__ = ['Parser', 'ParserError']
+
+from .error import MarkedYAMLError
+from .tokens import *
+from .events import *
+from .scanner import *
+
+class ParserError(MarkedYAMLError):
+    pass
+
+class Parser:
+    # Since writing a recursive-descendant parser is a straightforward task, we
+    # do not give many comments here.
+
+    DEFAULT_TAGS = {
+        '!':   '!',
+        '!!':  'tag:yaml.org,2002:',
+    }
+
+    def __init__(self):
+        self.current_event = None
+        self.yaml_version = None
+        self.tag_handles = {}
+        self.states = []
+        self.marks = []
+        self.state = self.parse_stream_start
+
+    def dispose(self):
+        # Reset the state attributes (to clear self-references)
+        self.states = []
+        self.state = None
+
+    def check_event(self, *choices):
+        # Check the type of the next event.
+        if self.current_event is None:
+            if self.state:
+                self.current_event = self.state()
+        if self.current_event is not None:
+            if not choices:
+                return True
+            for choice in choices:
+                if isinstance(self.current_event, choice):
+                    return True
+        return False
+
+    def peek_event(self):
+        # Get the next event.
+        if self.current_event is None:
+            if self.state:
+                self.current_event = self.state()
+        return self.current_event
+
+    def get_event(self):
+        # Get the next event and proceed further.
+        if self.current_event is None:
+            if self.state:
+                self.current_event = self.state()
+        value = self.current_event
+        self.current_event = None
+        return value
+
+    # stream    ::= STREAM-START implicit_document? explicit_document* STREAM-END
+    # implicit_document ::= block_node DOCUMENT-END*
+    # explicit_document ::= DIRECTIVE* DOCUMENT-START block_node? DOCUMENT-END*
+
+    def parse_stream_start(self):
+
+        # Parse the stream start.
+        token = self.get_token()
+        event = StreamStartEvent(token.start_mark, token.end_mark,
+                encoding=token.encoding)
+
+        # Prepare the next state.
+        self.state = self.parse_implicit_document_start
+
+        return event
+
+    def parse_implicit_document_start(self):
+
+        # Parse an implicit document.
+        if not self.check_token(DirectiveToken, DocumentStartToken,
+                StreamEndToken):
+            self.tag_handles = self.DEFAULT_TAGS
+            token = self.peek_token()
+            start_mark = end_mark = token.start_mark
+            event = DocumentStartEvent(start_mark, end_mark,
+                    explicit=False)
+
+            # Prepare the next state.
+            self.states.append(self.parse_document_end)
+            self.state = self.parse_block_node
+
+            return event
+
+        else:
+            return self.parse_document_start()
+
+    def parse_document_start(self):
+
+        # Parse any extra document end indicators.
+        while self.check_token(DocumentEndToken):
+            self.get_token()
+
+        # Parse an explicit document.
+        if not self.check_token(StreamEndToken):
+            token = self.peek_token()
+            start_mark = token.start_mark
+            version, tags = self.process_directives()
+            if not self.check_token(DocumentStartToken):
+                raise ParserError(None, None,
+                        "expected '<document start>', but found %r"
+                        % self.peek_token().id,
+                        self.peek_token().start_mark)
+            token = self.get_token()
+            end_mark = token.end_mark
+            event = DocumentStartEvent(start_mark, end_mark,
+                    explicit=True, version=version, tags=tags)
+            self.states.append(self.parse_document_end)
+            self.state = self.parse_document_content
+        else:
+            # Parse the end of the stream.
+            token = self.get_token()
+            event = StreamEndEvent(token.start_mark, token.end_mark)
+            assert not self.states
+            assert not self.marks
+            self.state = None
+        return event
+
+    def parse_document_end(self):
+
+        # Parse the document end.
+        token = self.peek_token()
+        start_mark = end_mark = token.start_mark
+        explicit = False
+        if self.check_token(DocumentEndToken):
+            token = self.get_token()
+            end_mark = token.end_mark
+            explicit = True
+        event = DocumentEndEvent(start_mark, end_mark,
+                explicit=explicit)
+
+        # Prepare the next state.
+        self.state = self.parse_document_start
+
+        return event
+
+    def parse_document_content(self):
+        if self.check_token(DirectiveToken,
+                DocumentStartToken, DocumentEndToken, StreamEndToken):
+            event = self.process_empty_scalar(self.peek_token().start_mark)
+            self.state = self.states.pop()
+            return event
+        else:
+            return self.parse_block_node()
+
+    def process_directives(self):
+        self.yaml_version = None
+        self.tag_handles = {}
+        while self.check_token(DirectiveToken):
+            token = self.get_token()
+            if token.name == 'YAML':
+                if self.yaml_version is not None:
+                    raise ParserError(None, None,
+                            "found duplicate YAML directive", token.start_mark)
+                major, minor = token.value
+                if major != 1:
+                    raise ParserError(None, None,
+                            "found incompatible YAML document (version 1.* is required)",
+                            token.start_mark)
+                self.yaml_version = token.value
+            elif token.name == 'TAG':
+                handle, prefix = token.value
+                if handle in self.tag_handles:
+                    raise ParserError(None, None,
+                            "duplicate tag handle %r" % handle,
+                            token.start_mark)
+                self.tag_handles[handle] = prefix
+        if self.tag_handles:
+            value = self.yaml_version, self.tag_handles.copy()
+        else:
+            value = self.yaml_version, None
+        for key in self.DEFAULT_TAGS:
+            if key not in self.tag_handles:
+                self.tag_handles[key] = self.DEFAULT_TAGS[key]
+        return value
+
+    # block_node_or_indentless_sequence ::= ALIAS
+    #               | properties (block_content | indentless_block_sequence)?
+    #               | block_content
+    #               | indentless_block_sequence
+    # block_node    ::= ALIAS
+    #                   | properties block_content?
+    #                   | block_content
+    # flow_node     ::= ALIAS
+    #                   | properties flow_content?
+    #                   | flow_content
+    # properties    ::= TAG ANCHOR? | ANCHOR TAG?
+    # block_content     ::= block_collection | flow_collection | SCALAR
+    # flow_content      ::= flow_collection | SCALAR
+    # block_collection  ::= block_sequence | block_mapping
+    # flow_collection   ::= flow_sequence | flow_mapping
+
+    def parse_block_node(self):
+        return self.parse_node(block=True)
+
+    def parse_flow_node(self):
+        return self.parse_node()
+
+    def parse_block_node_or_indentless_sequence(self):
+        return self.parse_node(block=True, indentless_sequence=True)
+
+    def parse_node(self, block=False, indentless_sequence=False):
+        if self.check_token(AliasToken):
+            token = self.get_token()
+            event = AliasEvent(token.value, token.start_mark, token.end_mark)
+            self.state = self.states.pop()
+        else:
+            anchor = None
+            tag = None
+            start_mark = end_mark = tag_mark = None
+            if self.check_token(AnchorToken):
+                token = self.get_token()
+                start_mark = token.start_mark
+                end_mark = token.end_mark
+                anchor = token.value
+                if self.check_token(TagToken):
+                    token = self.get_token()
+                    tag_mark = token.start_mark
+                    end_mark = token.end_mark
+                    tag = token.value
+            elif self.check_token(TagToken):
+                token = self.get_token()
+                start_mark = tag_mark = token.start_mark
+                end_mark = token.end_mark
+                tag = token.value
+                if self.check_token(AnchorToken):
+                    token = self.get_token()
+                    end_mark = token.end_mark
+                    anchor = token.value
+            if tag is not None:
+                handle, suffix = tag
+                if handle is not None:
+                    if handle not in self.tag_handles:
+                        raise ParserError("while parsing a node", start_mark,
+                                "found undefined tag handle %r" % handle,
+                                tag_mark)
+                    tag = self.tag_handles[handle]+suffix
+                else:
+                    tag = suffix
+            #if tag == '!':
+            #    raise ParserError("while parsing a node", start_mark,
+            #            "found non-specific tag '!'", tag_mark,
+            #            "Please check 'http://pyyaml.org/wiki/YAMLNonSpecificTag' and share your opinion.")
+            if start_mark is None:
+                start_mark = end_mark = self.peek_token().start_mark
+            event = None
+            implicit = (tag is None or tag == '!')
+            if indentless_sequence and self.check_token(BlockEntryToken):
+                end_mark = self.peek_token().end_mark
+                event = SequenceStartEvent(anchor, tag, implicit,
+                        start_mark, end_mark)
+                self.state = self.parse_indentless_sequence_entry
+            else:
+                if self.check_token(ScalarToken):
+                    token = self.get_token()
+                    end_mark = token.end_mark
+                    if (token.plain and tag is None) or tag == '!':
+                        implicit = (True, False)
+                    elif tag is None:
+                        implicit = (False, True)
+                    else:
+                        implicit = (False, False)
+                    event = ScalarEvent(anchor, tag, implicit, token.value,
+                            start_mark, end_mark, style=token.style)
+                    self.state = self.states.pop()
+                elif self.check_token(FlowSequenceStartToken):
+                    end_mark = self.peek_token().end_mark
+                    event = SequenceStartEvent(anchor, tag, implicit,
+                            start_mark, end_mark, flow_style=True)
+                    self.state = self.parse_flow_sequence_first_entry
+                elif self.check_token(FlowMappingStartToken):
+                    end_mark = self.peek_token().end_mark
+                    event = MappingStartEvent(anchor, tag, implicit,
+                            start_mark, end_mark, flow_style=True)
+                    self.state = self.parse_flow_mapping_first_key
+                elif block and self.check_token(BlockSequenceStartToken):
+                    end_mark = self.peek_token().start_mark
+                    event = SequenceStartEvent(anchor, tag, implicit,
+                            start_mark, end_mark, flow_style=False)
+                    self.state = self.parse_block_sequence_first_entry
+                elif block and self.check_token(BlockMappingStartToken):
+                    end_mark = self.peek_token().start_mark
+                    event = MappingStartEvent(anchor, tag, implicit,
+                            start_mark, end_mark, flow_style=False)
+                    self.state = self.parse_block_mapping_first_key
+                elif anchor is not None or tag is not None:
+                    # Empty scalars are allowed even if a tag or an anchor is
+                    # specified.
+                    event = ScalarEvent(anchor, tag, (implicit, False), '',
+                            start_mark, end_mark)
+                    self.state = self.states.pop()
+                else:
+                    if block:
+                        node = 'block'
+                    else:
+                        node = 'flow'
+                    token = self.peek_token()
+                    raise ParserError("while parsing a %s node" % node, start_mark,
+                            "expected the node content, but found %r" % token.id,
+                            token.start_mark)
+        return event
+
+    # block_sequence ::= BLOCK-SEQUENCE-START (BLOCK-ENTRY block_node?)* BLOCK-END
+
+    def parse_block_sequence_first_entry(self):
+        token = self.get_token()
+        self.marks.append(token.start_mark)
+        return self.parse_block_sequence_entry()
+
+    def parse_block_sequence_entry(self):
+        if self.check_token(BlockEntryToken):
+            token = self.get_token()
+            if not self.check_token(BlockEntryToken, BlockEndToken):
+                self.states.append(self.parse_block_sequence_entry)
+                return self.parse_block_node()
+            else:
+                self.state = self.parse_block_sequence_entry
+                return self.process_empty_scalar(token.end_mark)
+        if not self.check_token(BlockEndToken):
+            token = self.peek_token()
+            raise ParserError("while parsing a block collection", self.marks[-1],
+                    "expected <block end>, but found %r" % token.id, token.start_mark)
+        token = self.get_token()
+        event = SequenceEndEvent(token.start_mark, token.end_mark)
+        self.state = self.states.pop()
+        self.marks.pop()
+        return event
+
+    # indentless_sequence ::= (BLOCK-ENTRY block_node?)+
+
+    def parse_indentless_sequence_entry(self):
+        if self.check_token(BlockEntryToken):
+            token = self.get_token()
+            if not self.check_token(BlockEntryToken,
+                    KeyToken, ValueToken, BlockEndToken):
+                self.states.append(self.parse_indentless_sequence_entry)
+                return self.parse_block_node()
+            else:
+                self.state = self.parse_indentless_sequence_entry
+                return self.process_empty_scalar(token.end_mark)
+        token = self.peek_token()
+        event = SequenceEndEvent(token.start_mark, token.start_mark)
+        self.state = self.states.pop()
+        return event
+
+    # block_mapping     ::= BLOCK-MAPPING_START
+    #                       ((KEY block_node_or_indentless_sequence?)?
+    #                       (VALUE block_node_or_indentless_sequence?)?)*
+    #                       BLOCK-END
+
+    def parse_block_mapping_first_key(self):
+        token = self.get_token()
+        self.marks.append(token.start_mark)
+        return self.parse_block_mapping_key()
+
+    def parse_block_mapping_key(self):
+        if self.check_token(KeyToken):
+            token = self.get_token()
+            if not self.check_token(KeyToken, ValueToken, BlockEndToken):
+                self.states.append(self.parse_block_mapping_value)
+                return self.parse_block_node_or_indentless_sequence()
+            else:
+                self.state = self.parse_block_mapping_value
+                return self.process_empty_scalar(token.end_mark)
+        if not self.check_token(BlockEndToken):
+            token = self.peek_token()
+            raise ParserError("while parsing a block mapping", self.marks[-1],
+                    "expected <block end>, but found %r" % token.id, token.start_mark)
+        token = self.get_token()
+        event = MappingEndEvent(token.start_mark, token.end_mark)
+        self.state = self.states.pop()
+        self.marks.pop()
+        return event
+
+    def parse_block_mapping_value(self):
+        if self.check_token(ValueToken):
+            token = self.get_token()
+            if not self.check_token(KeyToken, ValueToken, BlockEndToken):
+                self.states.append(self.parse_block_mapping_key)
+                return self.parse_block_node_or_indentless_sequence()
+            else:
+                self.state = self.parse_block_mapping_key
+                return self.process_empty_scalar(token.end_mark)
+        else:
+            self.state = self.parse_block_mapping_key
+            token = self.peek_token()
+            return self.process_empty_scalar(token.start_mark)
+
+    # flow_sequence     ::= FLOW-SEQUENCE-START
+    #                       (flow_sequence_entry FLOW-ENTRY)*
+    #                       flow_sequence_entry?
+    #                       FLOW-SEQUENCE-END
+    # flow_sequence_entry   ::= flow_node | KEY flow_node? (VALUE flow_node?)?
+    #
+    # Note that while production rules for both flow_sequence_entry and
+    # flow_mapping_entry are equal, their interpretations are different.
+    # For `flow_sequence_entry`, the part `KEY flow_node? (VALUE flow_node?)?`
+    # generate an inline mapping (set syntax).
+
+    def parse_flow_sequence_first_entry(self):
+        token = self.get_token()
+        self.marks.append(token.start_mark)
+        return self.parse_flow_sequence_entry(first=True)
+
+    def parse_flow_sequence_entry(self, first=False):
+        if not self.check_token(FlowSequenceEndToken):
+            if not first:
+                if self.check_token(FlowEntryToken):
+                    self.get_token()
+                else:
+                    token = self.peek_token()
+                    raise ParserError("while parsing a flow sequence", self.marks[-1],
+                            "expected ',' or ']', but got %r" % token.id, token.start_mark)
+            
+            if self.check_token(KeyToken):
+                token = self.peek_token()
+                event = MappingStartEvent(None, None, True,
+                        token.start_mark, token.end_mark,
+                        flow_style=True)
+                self.state = self.parse_flow_sequence_entry_mapping_key
+                return event
+            elif not self.check_token(FlowSequenceEndToken):
+                self.states.append(self.parse_flow_sequence_entry)
+                return self.parse_flow_node()
+        token = self.get_token()
+        event = SequenceEndEvent(token.start_mark, token.end_mark)
+        self.state = self.states.pop()
+        self.marks.pop()
+        return event
+
+    def parse_flow_sequence_entry_mapping_key(self):
+        token = self.get_token()
+        if not self.check_token(ValueToken,
+                FlowEntryToken, FlowSequenceEndToken):
+            self.states.append(self.parse_flow_sequence_entry_mapping_value)
+            return self.parse_flow_node()
+        else:
+            self.state = self.parse_flow_sequence_entry_mapping_value
+            return self.process_empty_scalar(token.end_mark)
+
+    def parse_flow_sequence_entry_mapping_value(self):
+        if self.check_token(ValueToken):
+            token = self.get_token()
+            if not self.check_token(FlowEntryToken, FlowSequenceEndToken):
+                self.states.append(self.parse_flow_sequence_entry_mapping_end)
+                return self.parse_flow_node()
+            else:
+                self.state = self.parse_flow_sequence_entry_mapping_end
+                return self.process_empty_scalar(token.end_mark)
+        else:
+            self.state = self.parse_flow_sequence_entry_mapping_end
+            token = self.peek_token()
+            return self.process_empty_scalar(token.start_mark)
+
+    def parse_flow_sequence_entry_mapping_end(self):
+        self.state = self.parse_flow_sequence_entry
+        token = self.peek_token()
+        return MappingEndEvent(token.start_mark, token.start_mark)
+
+    # flow_mapping  ::= FLOW-MAPPING-START
+    #                   (flow_mapping_entry FLOW-ENTRY)*
+    #                   flow_mapping_entry?
+    #                   FLOW-MAPPING-END
+    # flow_mapping_entry    ::= flow_node | KEY flow_node? (VALUE flow_node?)?
+
+    def parse_flow_mapping_first_key(self):
+        token = self.get_token()
+        self.marks.append(token.start_mark)
+        return self.parse_flow_mapping_key(first=True)
+
+    def parse_flow_mapping_key(self, first=False):
+        if not self.check_token(FlowMappingEndToken):
+            if not first:
+                if self.check_token(FlowEntryToken):
+                    self.get_token()
+                else:
+                    token = self.peek_token()
+                    raise ParserError("while parsing a flow mapping", self.marks[-1],
+                            "expected ',' or '}', but got %r" % token.id, token.start_mark)
+            if self.check_token(KeyToken):
+                token = self.get_token()
+                if not self.check_token(ValueToken,
+                        FlowEntryToken, FlowMappingEndToken):
+                    self.states.append(self.parse_flow_mapping_value)
+                    return self.parse_flow_node()
+                else:
+                    self.state = self.parse_flow_mapping_value
+                    return self.process_empty_scalar(token.end_mark)
+            elif not self.check_token(FlowMappingEndToken):
+                self.states.append(self.parse_flow_mapping_empty_value)
+                return self.parse_flow_node()
+        token = self.get_token()
+        event = MappingEndEvent(token.start_mark, token.end_mark)
+        self.state = self.states.pop()
+        self.marks.pop()
+        return event
+
+    def parse_flow_mapping_value(self):
+        if self.check_token(ValueToken):
+            token = self.get_token()
+            if not self.check_token(FlowEntryToken, FlowMappingEndToken):
+                self.states.append(self.parse_flow_mapping_key)
+                return self.parse_flow_node()
+            else:
+                self.state = self.parse_flow_mapping_key
+                return self.process_empty_scalar(token.end_mark)
+        else:
+            self.state = self.parse_flow_mapping_key
+            token = self.peek_token()
+            return self.process_empty_scalar(token.start_mark)
+
+    def parse_flow_mapping_empty_value(self):
+        self.state = self.parse_flow_mapping_key
+        return self.process_empty_scalar(self.peek_token().start_mark)
+
+    def process_empty_scalar(self, mark):
+        return ScalarEvent(None, None, (True, False), '', mark, mark)
+
diff --git a/contrib/python/PyYAML/py3/yaml/reader.py b/contrib/python/PyYAML/py3/yaml/reader.py
index 79402a8352..774b0219b5 100644
--- a/contrib/python/PyYAML/py3/yaml/reader.py
+++ b/contrib/python/PyYAML/py3/yaml/reader.py
@@ -1,185 +1,185 @@
-# This module contains abstractions for the input stream. You don't have to 
-# looks further, there are no pretty code. 
-# 
-# We define two classes here. 
-# 
-#   Mark(source, line, column) 
-# It's just a record and its only use is producing nice error messages. 
-# Parser does not use it for any other purposes. 
-# 
-#   Reader(source, data) 
-# Reader determines the encoding of `data` and converts it to unicode. 
-# Reader provides the following methods and attributes: 
-#   reader.peek(length=1) - return the next `length` characters 
-#   reader.forward(length=1) - move the current position to `length` characters. 
-#   reader.index - the number of the current character. 
-#   reader.line, stream.column - the line and the column of the current character. 
- 
-__all__ = ['Reader', 'ReaderError'] 
- 
-from .error import YAMLError, Mark 
- 
-import codecs, re 
- 
-class ReaderError(YAMLError): 
- 
-    def __init__(self, name, position, character, encoding, reason): 
-        self.name = name 
-        self.character = character 
-        self.position = position 
-        self.encoding = encoding 
-        self.reason = reason 
- 
-    def __str__(self): 
-        if isinstance(self.character, bytes): 
-            return "'%s' codec can't decode byte #x%02x: %s\n"  \ 
-                    "  in \"%s\", position %d"    \ 
-                    % (self.encoding, ord(self.character), self.reason, 
-                            self.name, self.position) 
-        else: 
-            return "unacceptable character #x%04x: %s\n"    \ 
-                    "  in \"%s\", position %d"    \ 
-                    % (self.character, self.reason, 
-                            self.name, self.position) 
- 
-class Reader(object): 
-    # Reader: 
-    # - determines the data encoding and converts it to a unicode string, 
-    # - checks if characters are in allowed range, 
-    # - adds '\0' to the end. 
- 
-    # Reader accepts 
-    #  - a `bytes` object, 
-    #  - a `str` object, 
-    #  - a file-like object with its `read` method returning `str`, 
-    #  - a file-like object with its `read` method returning `unicode`. 
- 
-    # Yeah, it's ugly and slow. 
- 
-    def __init__(self, stream): 
-        self.name = None 
-        self.stream = None 
-        self.stream_pointer = 0 
-        self.eof = True 
-        self.buffer = '' 
-        self.pointer = 0 
-        self.raw_buffer = None 
-        self.raw_decode = None 
-        self.encoding = None 
-        self.index = 0 
-        self.line = 0 
-        self.column = 0 
-        if isinstance(stream, str): 
-            self.name = "<unicode string>" 
-            self.check_printable(stream) 
-            self.buffer = stream+'\0' 
-        elif isinstance(stream, bytes): 
-            self.name = "<byte string>" 
-            self.raw_buffer = stream 
-            self.determine_encoding() 
-        else: 
-            self.stream = stream 
-            self.name = getattr(stream, 'name', "<file>") 
-            self.eof = False 
-            self.raw_buffer = None 
-            self.determine_encoding() 
- 
-    def peek(self, index=0): 
-        try: 
-            return self.buffer[self.pointer+index] 
-        except IndexError: 
-            self.update(index+1) 
-            return self.buffer[self.pointer+index] 
- 
-    def prefix(self, length=1): 
-        if self.pointer+length >= len(self.buffer): 
-            self.update(length) 
-        return self.buffer[self.pointer:self.pointer+length] 
- 
-    def forward(self, length=1): 
-        if self.pointer+length+1 >= len(self.buffer): 
-            self.update(length+1) 
-        while length: 
-            ch = self.buffer[self.pointer] 
-            self.pointer += 1 
-            self.index += 1 
-            if ch in '\n\x85\u2028\u2029'  \ 
-                    or (ch == '\r' and self.buffer[self.pointer] != '\n'): 
-                self.line += 1 
-                self.column = 0 
-            elif ch != '\uFEFF': 
-                self.column += 1 
-            length -= 1 
- 
-    def get_mark(self): 
-        if self.stream is None: 
-            return Mark(self.name, self.index, self.line, self.column, 
-                    self.buffer, self.pointer) 
-        else: 
-            return Mark(self.name, self.index, self.line, self.column, 
-                    None, None) 
- 
-    def determine_encoding(self): 
-        while not self.eof and (self.raw_buffer is None or len(self.raw_buffer) < 2): 
-            self.update_raw() 
-        if isinstance(self.raw_buffer, bytes): 
-            if self.raw_buffer.startswith(codecs.BOM_UTF16_LE): 
-                self.raw_decode = codecs.utf_16_le_decode 
-                self.encoding = 'utf-16-le' 
-            elif self.raw_buffer.startswith(codecs.BOM_UTF16_BE): 
-                self.raw_decode = codecs.utf_16_be_decode 
-                self.encoding = 'utf-16-be' 
-            else: 
-                self.raw_decode = codecs.utf_8_decode 
-                self.encoding = 'utf-8' 
-        self.update(1) 
- 
+# This module contains abstractions for the input stream. You don't have to
+# looks further, there are no pretty code.
+#
+# We define two classes here.
+#
+#   Mark(source, line, column)
+# It's just a record and its only use is producing nice error messages.
+# Parser does not use it for any other purposes.
+#
+#   Reader(source, data)
+# Reader determines the encoding of `data` and converts it to unicode.
+# Reader provides the following methods and attributes:
+#   reader.peek(length=1) - return the next `length` characters
+#   reader.forward(length=1) - move the current position to `length` characters.
+#   reader.index - the number of the current character.
+#   reader.line, stream.column - the line and the column of the current character.
+
+__all__ = ['Reader', 'ReaderError']
+
+from .error import YAMLError, Mark
+
+import codecs, re
+
+class ReaderError(YAMLError):
+
+    def __init__(self, name, position, character, encoding, reason):
+        self.name = name
+        self.character = character
+        self.position = position
+        self.encoding = encoding
+        self.reason = reason
+
+    def __str__(self):
+        if isinstance(self.character, bytes):
+            return "'%s' codec can't decode byte #x%02x: %s\n"  \
+                    "  in \"%s\", position %d"    \
+                    % (self.encoding, ord(self.character), self.reason,
+                            self.name, self.position)
+        else:
+            return "unacceptable character #x%04x: %s\n"    \
+                    "  in \"%s\", position %d"    \
+                    % (self.character, self.reason,
+                            self.name, self.position)
+
+class Reader(object):
+    # Reader:
+    # - determines the data encoding and converts it to a unicode string,
+    # - checks if characters are in allowed range,
+    # - adds '\0' to the end.
+
+    # Reader accepts
+    #  - a `bytes` object,
+    #  - a `str` object,
+    #  - a file-like object with its `read` method returning `str`,
+    #  - a file-like object with its `read` method returning `unicode`.
+
+    # Yeah, it's ugly and slow.
+
+    def __init__(self, stream):
+        self.name = None
+        self.stream = None
+        self.stream_pointer = 0
+        self.eof = True
+        self.buffer = ''
+        self.pointer = 0
+        self.raw_buffer = None
+        self.raw_decode = None
+        self.encoding = None
+        self.index = 0
+        self.line = 0
+        self.column = 0
+        if isinstance(stream, str):
+            self.name = "<unicode string>"
+            self.check_printable(stream)
+            self.buffer = stream+'\0'
+        elif isinstance(stream, bytes):
+            self.name = "<byte string>"
+            self.raw_buffer = stream
+            self.determine_encoding()
+        else:
+            self.stream = stream
+            self.name = getattr(stream, 'name', "<file>")
+            self.eof = False
+            self.raw_buffer = None
+            self.determine_encoding()
+
+    def peek(self, index=0):
+        try:
+            return self.buffer[self.pointer+index]
+        except IndexError:
+            self.update(index+1)
+            return self.buffer[self.pointer+index]
+
+    def prefix(self, length=1):
+        if self.pointer+length >= len(self.buffer):
+            self.update(length)
+        return self.buffer[self.pointer:self.pointer+length]
+
+    def forward(self, length=1):
+        if self.pointer+length+1 >= len(self.buffer):
+            self.update(length+1)
+        while length:
+            ch = self.buffer[self.pointer]
+            self.pointer += 1
+            self.index += 1
+            if ch in '\n\x85\u2028\u2029'  \
+                    or (ch == '\r' and self.buffer[self.pointer] != '\n'):
+                self.line += 1
+                self.column = 0
+            elif ch != '\uFEFF':
+                self.column += 1
+            length -= 1
+
+    def get_mark(self):
+        if self.stream is None:
+            return Mark(self.name, self.index, self.line, self.column,
+                    self.buffer, self.pointer)
+        else:
+            return Mark(self.name, self.index, self.line, self.column,
+                    None, None)
+
+    def determine_encoding(self):
+        while not self.eof and (self.raw_buffer is None or len(self.raw_buffer) < 2):
+            self.update_raw()
+        if isinstance(self.raw_buffer, bytes):
+            if self.raw_buffer.startswith(codecs.BOM_UTF16_LE):
+                self.raw_decode = codecs.utf_16_le_decode
+                self.encoding = 'utf-16-le'
+            elif self.raw_buffer.startswith(codecs.BOM_UTF16_BE):
+                self.raw_decode = codecs.utf_16_be_decode
+                self.encoding = 'utf-16-be'
+            else:
+                self.raw_decode = codecs.utf_8_decode
+                self.encoding = 'utf-8'
+        self.update(1)
+
     NON_PRINTABLE = re.compile('[^\x09\x0A\x0D\x20-\x7E\x85\xA0-\uD7FF\uE000-\uFFFD\U00010000-\U0010ffff]')
-    def check_printable(self, data): 
-        match = self.NON_PRINTABLE.search(data) 
-        if match: 
-            character = match.group() 
-            position = self.index+(len(self.buffer)-self.pointer)+match.start() 
-            raise ReaderError(self.name, position, ord(character), 
-                    'unicode', "special characters are not allowed") 
- 
-    def update(self, length): 
-        if self.raw_buffer is None: 
-            return 
-        self.buffer = self.buffer[self.pointer:] 
-        self.pointer = 0 
-        while len(self.buffer) < length: 
-            if not self.eof: 
-                self.update_raw() 
-            if self.raw_decode is not None: 
-                try: 
-                    data, converted = self.raw_decode(self.raw_buffer, 
-                            'strict', self.eof) 
-                except UnicodeDecodeError as exc: 
-                    character = self.raw_buffer[exc.start] 
-                    if self.stream is not None: 
-                        position = self.stream_pointer-len(self.raw_buffer)+exc.start 
-                    else: 
-                        position = exc.start 
-                    raise ReaderError(self.name, position, character, 
-                            exc.encoding, exc.reason) 
-            else: 
-                data = self.raw_buffer 
-                converted = len(data) 
-            self.check_printable(data) 
-            self.buffer += data 
-            self.raw_buffer = self.raw_buffer[converted:] 
-            if self.eof: 
-                self.buffer += '\0' 
-                self.raw_buffer = None 
-                break 
- 
-    def update_raw(self, size=4096): 
-        data = self.stream.read(size) 
-        if self.raw_buffer is None: 
-            self.raw_buffer = data 
-        else: 
-            self.raw_buffer += data 
-        self.stream_pointer += len(data) 
-        if not data: 
-            self.eof = True 
+    def check_printable(self, data):
+        match = self.NON_PRINTABLE.search(data)
+        if match:
+            character = match.group()
+            position = self.index+(len(self.buffer)-self.pointer)+match.start()
+            raise ReaderError(self.name, position, ord(character),
+                    'unicode', "special characters are not allowed")
+
+    def update(self, length):
+        if self.raw_buffer is None:
+            return
+        self.buffer = self.buffer[self.pointer:]
+        self.pointer = 0
+        while len(self.buffer) < length:
+            if not self.eof:
+                self.update_raw()
+            if self.raw_decode is not None:
+                try:
+                    data, converted = self.raw_decode(self.raw_buffer,
+                            'strict', self.eof)
+                except UnicodeDecodeError as exc:
+                    character = self.raw_buffer[exc.start]
+                    if self.stream is not None:
+                        position = self.stream_pointer-len(self.raw_buffer)+exc.start
+                    else:
+                        position = exc.start
+                    raise ReaderError(self.name, position, character,
+                            exc.encoding, exc.reason)
+            else:
+                data = self.raw_buffer
+                converted = len(data)
+            self.check_printable(data)
+            self.buffer += data
+            self.raw_buffer = self.raw_buffer[converted:]
+            if self.eof:
+                self.buffer += '\0'
+                self.raw_buffer = None
+                break
+
+    def update_raw(self, size=4096):
+        data = self.stream.read(size)
+        if self.raw_buffer is None:
+            self.raw_buffer = data
+        else:
+            self.raw_buffer += data
+        self.stream_pointer += len(data)
+        if not data:
+            self.eof = True
diff --git a/contrib/python/PyYAML/py3/yaml/representer.py b/contrib/python/PyYAML/py3/yaml/representer.py
index 9011a55faf..8d0d1fe251 100644
--- a/contrib/python/PyYAML/py3/yaml/representer.py
+++ b/contrib/python/PyYAML/py3/yaml/representer.py
@@ -1,389 +1,389 @@
- 
-__all__ = ['BaseRepresenter', 'SafeRepresenter', 'Representer', 
-    'RepresenterError'] 
- 
-from .error import * 
-from .nodes import * 
- 
+
+__all__ = ['BaseRepresenter', 'SafeRepresenter', 'Representer',
+    'RepresenterError']
+
+from .error import *
+from .nodes import *
+
 import datetime, copyreg, types, base64, collections
- 
-class RepresenterError(YAMLError): 
-    pass 
- 
-class BaseRepresenter: 
- 
-    yaml_representers = {} 
-    yaml_multi_representers = {} 
- 
+
+class RepresenterError(YAMLError):
+    pass
+
+class BaseRepresenter:
+
+    yaml_representers = {}
+    yaml_multi_representers = {}
+
     def __init__(self, default_style=None, default_flow_style=False, sort_keys=True):
-        self.default_style = default_style 
+        self.default_style = default_style
         self.sort_keys = sort_keys
-        self.default_flow_style = default_flow_style 
-        self.represented_objects = {} 
-        self.object_keeper = [] 
-        self.alias_key = None 
- 
-    def represent(self, data): 
-        node = self.represent_data(data) 
-        self.serialize(node) 
-        self.represented_objects = {} 
-        self.object_keeper = [] 
-        self.alias_key = None 
- 
-    def represent_data(self, data): 
-        if self.ignore_aliases(data): 
-            self.alias_key = None 
-        else: 
-            self.alias_key = id(data) 
-        if self.alias_key is not None: 
-            if self.alias_key in self.represented_objects: 
-                node = self.represented_objects[self.alias_key] 
-                #if node is None: 
-                #    raise RepresenterError("recursive objects are not allowed: %r" % data) 
-                return node 
-            #self.represented_objects[alias_key] = None 
-            self.object_keeper.append(data) 
-        data_types = type(data).__mro__ 
-        if data_types[0] in self.yaml_representers: 
-            node = self.yaml_representers[data_types[0]](self, data) 
-        else: 
-            for data_type in data_types: 
-                if data_type in self.yaml_multi_representers: 
-                    node = self.yaml_multi_representers[data_type](self, data) 
-                    break 
-            else: 
-                if None in self.yaml_multi_representers: 
-                    node = self.yaml_multi_representers[None](self, data) 
-                elif None in self.yaml_representers: 
-                    node = self.yaml_representers[None](self, data) 
-                else: 
-                    node = ScalarNode(None, str(data)) 
-        #if alias_key is not None: 
-        #    self.represented_objects[alias_key] = node 
-        return node 
- 
-    @classmethod 
-    def add_representer(cls, data_type, representer): 
-        if not 'yaml_representers' in cls.__dict__: 
-            cls.yaml_representers = cls.yaml_representers.copy() 
-        cls.yaml_representers[data_type] = representer 
- 
-    @classmethod 
-    def add_multi_representer(cls, data_type, representer): 
-        if not 'yaml_multi_representers' in cls.__dict__: 
-            cls.yaml_multi_representers = cls.yaml_multi_representers.copy() 
-        cls.yaml_multi_representers[data_type] = representer 
- 
-    def represent_scalar(self, tag, value, style=None): 
-        if style is None: 
-            style = self.default_style 
-        node = ScalarNode(tag, value, style=style) 
-        if self.alias_key is not None: 
-            self.represented_objects[self.alias_key] = node 
-        return node 
- 
-    def represent_sequence(self, tag, sequence, flow_style=None): 
-        value = [] 
-        node = SequenceNode(tag, value, flow_style=flow_style) 
-        if self.alias_key is not None: 
-            self.represented_objects[self.alias_key] = node 
-        best_style = True 
-        for item in sequence: 
-            node_item = self.represent_data(item) 
-            if not (isinstance(node_item, ScalarNode) and not node_item.style): 
-                best_style = False 
-            value.append(node_item) 
-        if flow_style is None: 
-            if self.default_flow_style is not None: 
-                node.flow_style = self.default_flow_style 
-            else: 
-                node.flow_style = best_style 
-        return node 
- 
-    def represent_mapping(self, tag, mapping, flow_style=None): 
-        value = [] 
-        node = MappingNode(tag, value, flow_style=flow_style) 
-        if self.alias_key is not None: 
-            self.represented_objects[self.alias_key] = node 
-        best_style = True 
-        if hasattr(mapping, 'items'): 
-            mapping = list(mapping.items()) 
+        self.default_flow_style = default_flow_style
+        self.represented_objects = {}
+        self.object_keeper = []
+        self.alias_key = None
+
+    def represent(self, data):
+        node = self.represent_data(data)
+        self.serialize(node)
+        self.represented_objects = {}
+        self.object_keeper = []
+        self.alias_key = None
+
+    def represent_data(self, data):
+        if self.ignore_aliases(data):
+            self.alias_key = None
+        else:
+            self.alias_key = id(data)
+        if self.alias_key is not None:
+            if self.alias_key in self.represented_objects:
+                node = self.represented_objects[self.alias_key]
+                #if node is None:
+                #    raise RepresenterError("recursive objects are not allowed: %r" % data)
+                return node
+            #self.represented_objects[alias_key] = None
+            self.object_keeper.append(data)
+        data_types = type(data).__mro__
+        if data_types[0] in self.yaml_representers:
+            node = self.yaml_representers[data_types[0]](self, data)
+        else:
+            for data_type in data_types:
+                if data_type in self.yaml_multi_representers:
+                    node = self.yaml_multi_representers[data_type](self, data)
+                    break
+            else:
+                if None in self.yaml_multi_representers:
+                    node = self.yaml_multi_representers[None](self, data)
+                elif None in self.yaml_representers:
+                    node = self.yaml_representers[None](self, data)
+                else:
+                    node = ScalarNode(None, str(data))
+        #if alias_key is not None:
+        #    self.represented_objects[alias_key] = node
+        return node
+
+    @classmethod
+    def add_representer(cls, data_type, representer):
+        if not 'yaml_representers' in cls.__dict__:
+            cls.yaml_representers = cls.yaml_representers.copy()
+        cls.yaml_representers[data_type] = representer
+
+    @classmethod
+    def add_multi_representer(cls, data_type, representer):
+        if not 'yaml_multi_representers' in cls.__dict__:
+            cls.yaml_multi_representers = cls.yaml_multi_representers.copy()
+        cls.yaml_multi_representers[data_type] = representer
+
+    def represent_scalar(self, tag, value, style=None):
+        if style is None:
+            style = self.default_style
+        node = ScalarNode(tag, value, style=style)
+        if self.alias_key is not None:
+            self.represented_objects[self.alias_key] = node
+        return node
+
+    def represent_sequence(self, tag, sequence, flow_style=None):
+        value = []
+        node = SequenceNode(tag, value, flow_style=flow_style)
+        if self.alias_key is not None:
+            self.represented_objects[self.alias_key] = node
+        best_style = True
+        for item in sequence:
+            node_item = self.represent_data(item)
+            if not (isinstance(node_item, ScalarNode) and not node_item.style):
+                best_style = False
+            value.append(node_item)
+        if flow_style is None:
+            if self.default_flow_style is not None:
+                node.flow_style = self.default_flow_style
+            else:
+                node.flow_style = best_style
+        return node
+
+    def represent_mapping(self, tag, mapping, flow_style=None):
+        value = []
+        node = MappingNode(tag, value, flow_style=flow_style)
+        if self.alias_key is not None:
+            self.represented_objects[self.alias_key] = node
+        best_style = True
+        if hasattr(mapping, 'items'):
+            mapping = list(mapping.items())
             if self.sort_keys:
                 try:
                     mapping = sorted(mapping)
                 except TypeError:
                     pass
-        for item_key, item_value in mapping: 
-            node_key = self.represent_data(item_key) 
-            node_value = self.represent_data(item_value) 
-            if not (isinstance(node_key, ScalarNode) and not node_key.style): 
-                best_style = False 
-            if not (isinstance(node_value, ScalarNode) and not node_value.style): 
-                best_style = False 
-            value.append((node_key, node_value)) 
-        if flow_style is None: 
-            if self.default_flow_style is not None: 
-                node.flow_style = self.default_flow_style 
-            else: 
-                node.flow_style = best_style 
-        return node 
- 
-    def ignore_aliases(self, data): 
-        return False 
- 
-class SafeRepresenter(BaseRepresenter): 
- 
-    def ignore_aliases(self, data): 
-        if data is None: 
-            return True 
-        if isinstance(data, tuple) and data == (): 
-            return True 
-        if isinstance(data, (str, bytes, bool, int, float)): 
-            return True 
- 
-    def represent_none(self, data): 
-        return self.represent_scalar('tag:yaml.org,2002:null', 'null') 
- 
-    def represent_str(self, data): 
+        for item_key, item_value in mapping:
+            node_key = self.represent_data(item_key)
+            node_value = self.represent_data(item_value)
+            if not (isinstance(node_key, ScalarNode) and not node_key.style):
+                best_style = False
+            if not (isinstance(node_value, ScalarNode) and not node_value.style):
+                best_style = False
+            value.append((node_key, node_value))
+        if flow_style is None:
+            if self.default_flow_style is not None:
+                node.flow_style = self.default_flow_style
+            else:
+                node.flow_style = best_style
+        return node
+
+    def ignore_aliases(self, data):
+        return False
+
+class SafeRepresenter(BaseRepresenter):
+
+    def ignore_aliases(self, data):
+        if data is None:
+            return True
+        if isinstance(data, tuple) and data == ():
+            return True
+        if isinstance(data, (str, bytes, bool, int, float)):
+            return True
+
+    def represent_none(self, data):
+        return self.represent_scalar('tag:yaml.org,2002:null', 'null')
+
+    def represent_str(self, data):
         return self.represent_scalar('tag:yaml.org,2002:str', str(data))
- 
-    def represent_binary(self, data): 
-        if hasattr(base64, 'encodebytes'): 
-            data = base64.encodebytes(data).decode('ascii') 
-        else: 
-            data = base64.encodestring(data).decode('ascii') 
-        return self.represent_scalar('tag:yaml.org,2002:binary', data, style='|') 
- 
-    def represent_bool(self, data): 
-        if data: 
-            value = 'true' 
-        else: 
-            value = 'false' 
-        return self.represent_scalar('tag:yaml.org,2002:bool', value) 
- 
-    def represent_int(self, data): 
-        return self.represent_scalar('tag:yaml.org,2002:int', str(data)) 
- 
-    inf_value = 1e300 
-    while repr(inf_value) != repr(inf_value*inf_value): 
-        inf_value *= inf_value 
- 
-    def represent_float(self, data): 
-        if data != data or (data == 0.0 and data == 1.0): 
-            value = '.nan' 
-        elif data == self.inf_value: 
-            value = '.inf' 
-        elif data == -self.inf_value: 
-            value = '-.inf' 
-        else: 
-            value = repr(data).lower() 
-            # Note that in some cases `repr(data)` represents a float number 
-            # without the decimal parts.  For instance: 
-            #   >>> repr(1e17) 
-            #   '1e17' 
-            # Unfortunately, this is not a valid float representation according 
-            # to the definition of the `!!float` tag.  We fix this by adding 
-            # '.0' before the 'e' symbol. 
-            if '.' not in value and 'e' in value: 
-                value = value.replace('e', '.0e', 1) 
-        return self.represent_scalar('tag:yaml.org,2002:float', value) 
- 
-    def represent_list(self, data): 
-        #pairs = (len(data) > 0 and isinstance(data, list)) 
-        #if pairs: 
-        #    for item in data: 
-        #        if not isinstance(item, tuple) or len(item) != 2: 
-        #            pairs = False 
-        #            break 
-        #if not pairs: 
-            return self.represent_sequence('tag:yaml.org,2002:seq', data) 
-        #value = [] 
-        #for item_key, item_value in data: 
-        #    value.append(self.represent_mapping(u'tag:yaml.org,2002:map', 
-        #        [(item_key, item_value)])) 
-        #return SequenceNode(u'tag:yaml.org,2002:pairs', value) 
- 
-    def represent_dict(self, data): 
-        return self.represent_mapping('tag:yaml.org,2002:map', data) 
- 
-    def represent_set(self, data): 
-        value = {} 
-        for key in data: 
-            value[key] = None 
-        return self.represent_mapping('tag:yaml.org,2002:set', value) 
- 
-    def represent_date(self, data): 
-        value = data.isoformat() 
-        return self.represent_scalar('tag:yaml.org,2002:timestamp', value) 
- 
-    def represent_datetime(self, data): 
-        value = data.isoformat(' ') 
-        return self.represent_scalar('tag:yaml.org,2002:timestamp', value) 
- 
-    def represent_yaml_object(self, tag, data, cls, flow_style=None): 
-        if hasattr(data, '__getstate__'): 
-            state = data.__getstate__() 
-        else: 
-            state = data.__dict__.copy() 
-        return self.represent_mapping(tag, state, flow_style=flow_style) 
- 
-    def represent_undefined(self, data): 
+
+    def represent_binary(self, data):
+        if hasattr(base64, 'encodebytes'):
+            data = base64.encodebytes(data).decode('ascii')
+        else:
+            data = base64.encodestring(data).decode('ascii')
+        return self.represent_scalar('tag:yaml.org,2002:binary', data, style='|')
+
+    def represent_bool(self, data):
+        if data:
+            value = 'true'
+        else:
+            value = 'false'
+        return self.represent_scalar('tag:yaml.org,2002:bool', value)
+
+    def represent_int(self, data):
+        return self.represent_scalar('tag:yaml.org,2002:int', str(data))
+
+    inf_value = 1e300
+    while repr(inf_value) != repr(inf_value*inf_value):
+        inf_value *= inf_value
+
+    def represent_float(self, data):
+        if data != data or (data == 0.0 and data == 1.0):
+            value = '.nan'
+        elif data == self.inf_value:
+            value = '.inf'
+        elif data == -self.inf_value:
+            value = '-.inf'
+        else:
+            value = repr(data).lower()
+            # Note that in some cases `repr(data)` represents a float number
+            # without the decimal parts.  For instance:
+            #   >>> repr(1e17)
+            #   '1e17'
+            # Unfortunately, this is not a valid float representation according
+            # to the definition of the `!!float` tag.  We fix this by adding
+            # '.0' before the 'e' symbol.
+            if '.' not in value and 'e' in value:
+                value = value.replace('e', '.0e', 1)
+        return self.represent_scalar('tag:yaml.org,2002:float', value)
+
+    def represent_list(self, data):
+        #pairs = (len(data) > 0 and isinstance(data, list))
+        #if pairs:
+        #    for item in data:
+        #        if not isinstance(item, tuple) or len(item) != 2:
+        #            pairs = False
+        #            break
+        #if not pairs:
+            return self.represent_sequence('tag:yaml.org,2002:seq', data)
+        #value = []
+        #for item_key, item_value in data:
+        #    value.append(self.represent_mapping(u'tag:yaml.org,2002:map',
+        #        [(item_key, item_value)]))
+        #return SequenceNode(u'tag:yaml.org,2002:pairs', value)
+
+    def represent_dict(self, data):
+        return self.represent_mapping('tag:yaml.org,2002:map', data)
+
+    def represent_set(self, data):
+        value = {}
+        for key in data:
+            value[key] = None
+        return self.represent_mapping('tag:yaml.org,2002:set', value)
+
+    def represent_date(self, data):
+        value = data.isoformat()
+        return self.represent_scalar('tag:yaml.org,2002:timestamp', value)
+
+    def represent_datetime(self, data):
+        value = data.isoformat(' ')
+        return self.represent_scalar('tag:yaml.org,2002:timestamp', value)
+
+    def represent_yaml_object(self, tag, data, cls, flow_style=None):
+        if hasattr(data, '__getstate__'):
+            state = data.__getstate__()
+        else:
+            state = data.__dict__.copy()
+        return self.represent_mapping(tag, state, flow_style=flow_style)
+
+    def represent_undefined(self, data):
         raise RepresenterError("cannot represent an object", data)
- 
-SafeRepresenter.add_representer(type(None), 
-        SafeRepresenter.represent_none) 
- 
-SafeRepresenter.add_representer(str, 
-        SafeRepresenter.represent_str) 
- 
-SafeRepresenter.add_representer(bytes, 
-        SafeRepresenter.represent_binary) 
- 
-SafeRepresenter.add_representer(bool, 
-        SafeRepresenter.represent_bool) 
- 
-SafeRepresenter.add_representer(int, 
-        SafeRepresenter.represent_int) 
- 
-SafeRepresenter.add_representer(float, 
-        SafeRepresenter.represent_float) 
- 
-SafeRepresenter.add_representer(list, 
-        SafeRepresenter.represent_list) 
- 
-SafeRepresenter.add_representer(tuple, 
-        SafeRepresenter.represent_list) 
- 
-SafeRepresenter.add_representer(dict, 
-        SafeRepresenter.represent_dict) 
- 
-SafeRepresenter.add_representer(set, 
-        SafeRepresenter.represent_set) 
- 
-SafeRepresenter.add_representer(datetime.date, 
-        SafeRepresenter.represent_date) 
- 
-SafeRepresenter.add_representer(datetime.datetime, 
-        SafeRepresenter.represent_datetime) 
- 
-SafeRepresenter.add_representer(None, 
-        SafeRepresenter.represent_undefined) 
- 
-class Representer(SafeRepresenter): 
- 
-    def represent_complex(self, data): 
-        if data.imag == 0.0: 
-            data = '%r' % data.real 
-        elif data.real == 0.0: 
-            data = '%rj' % data.imag 
-        elif data.imag > 0: 
-            data = '%r+%rj' % (data.real, data.imag) 
-        else: 
-            data = '%r%rj' % (data.real, data.imag) 
-        return self.represent_scalar('tag:yaml.org,2002:python/complex', data) 
- 
-    def represent_tuple(self, data): 
-        return self.represent_sequence('tag:yaml.org,2002:python/tuple', data) 
- 
-    def represent_name(self, data): 
-        name = '%s.%s' % (data.__module__, data.__name__) 
-        return self.represent_scalar('tag:yaml.org,2002:python/name:'+name, '') 
- 
-    def represent_module(self, data): 
-        return self.represent_scalar( 
-                'tag:yaml.org,2002:python/module:'+data.__name__, '') 
- 
-    def represent_object(self, data): 
-        # We use __reduce__ API to save the data. data.__reduce__ returns 
-        # a tuple of length 2-5: 
-        #   (function, args, state, listitems, dictitems) 
- 
-        # For reconstructing, we calls function(*args), then set its state, 
-        # listitems, and dictitems if they are not None. 
- 
-        # A special case is when function.__name__ == '__newobj__'. In this 
-        # case we create the object with args[0].__new__(*args). 
- 
-        # Another special case is when __reduce__ returns a string - we don't 
-        # support it. 
- 
-        # We produce a !!python/object, !!python/object/new or 
-        # !!python/object/apply node. 
- 
-        cls = type(data) 
-        if cls in copyreg.dispatch_table: 
-            reduce = copyreg.dispatch_table[cls](data) 
-        elif hasattr(data, '__reduce_ex__'): 
-            reduce = data.__reduce_ex__(2) 
-        elif hasattr(data, '__reduce__'): 
-            reduce = data.__reduce__() 
-        else: 
+
+SafeRepresenter.add_representer(type(None),
+        SafeRepresenter.represent_none)
+
+SafeRepresenter.add_representer(str,
+        SafeRepresenter.represent_str)
+
+SafeRepresenter.add_representer(bytes,
+        SafeRepresenter.represent_binary)
+
+SafeRepresenter.add_representer(bool,
+        SafeRepresenter.represent_bool)
+
+SafeRepresenter.add_representer(int,
+        SafeRepresenter.represent_int)
+
+SafeRepresenter.add_representer(float,
+        SafeRepresenter.represent_float)
+
+SafeRepresenter.add_representer(list,
+        SafeRepresenter.represent_list)
+
+SafeRepresenter.add_representer(tuple,
+        SafeRepresenter.represent_list)
+
+SafeRepresenter.add_representer(dict,
+        SafeRepresenter.represent_dict)
+
+SafeRepresenter.add_representer(set,
+        SafeRepresenter.represent_set)
+
+SafeRepresenter.add_representer(datetime.date,
+        SafeRepresenter.represent_date)
+
+SafeRepresenter.add_representer(datetime.datetime,
+        SafeRepresenter.represent_datetime)
+
+SafeRepresenter.add_representer(None,
+        SafeRepresenter.represent_undefined)
+
+class Representer(SafeRepresenter):
+
+    def represent_complex(self, data):
+        if data.imag == 0.0:
+            data = '%r' % data.real
+        elif data.real == 0.0:
+            data = '%rj' % data.imag
+        elif data.imag > 0:
+            data = '%r+%rj' % (data.real, data.imag)
+        else:
+            data = '%r%rj' % (data.real, data.imag)
+        return self.represent_scalar('tag:yaml.org,2002:python/complex', data)
+
+    def represent_tuple(self, data):
+        return self.represent_sequence('tag:yaml.org,2002:python/tuple', data)
+
+    def represent_name(self, data):
+        name = '%s.%s' % (data.__module__, data.__name__)
+        return self.represent_scalar('tag:yaml.org,2002:python/name:'+name, '')
+
+    def represent_module(self, data):
+        return self.represent_scalar(
+                'tag:yaml.org,2002:python/module:'+data.__name__, '')
+
+    def represent_object(self, data):
+        # We use __reduce__ API to save the data. data.__reduce__ returns
+        # a tuple of length 2-5:
+        #   (function, args, state, listitems, dictitems)
+
+        # For reconstructing, we calls function(*args), then set its state,
+        # listitems, and dictitems if they are not None.
+
+        # A special case is when function.__name__ == '__newobj__'. In this
+        # case we create the object with args[0].__new__(*args).
+
+        # Another special case is when __reduce__ returns a string - we don't
+        # support it.
+
+        # We produce a !!python/object, !!python/object/new or
+        # !!python/object/apply node.
+
+        cls = type(data)
+        if cls in copyreg.dispatch_table:
+            reduce = copyreg.dispatch_table[cls](data)
+        elif hasattr(data, '__reduce_ex__'):
+            reduce = data.__reduce_ex__(2)
+        elif hasattr(data, '__reduce__'):
+            reduce = data.__reduce__()
+        else:
             raise RepresenterError("cannot represent an object", data)
-        reduce = (list(reduce)+[None]*5)[:5] 
-        function, args, state, listitems, dictitems = reduce 
-        args = list(args) 
-        if state is None: 
-            state = {} 
-        if listitems is not None: 
-            listitems = list(listitems) 
-        if dictitems is not None: 
-            dictitems = dict(dictitems) 
-        if function.__name__ == '__newobj__': 
-            function = args[0] 
-            args = args[1:] 
-            tag = 'tag:yaml.org,2002:python/object/new:' 
-            newobj = True 
-        else: 
-            tag = 'tag:yaml.org,2002:python/object/apply:' 
-            newobj = False 
-        function_name = '%s.%s' % (function.__module__, function.__name__) 
-        if not args and not listitems and not dictitems \ 
-                and isinstance(state, dict) and newobj: 
-            return self.represent_mapping( 
-                    'tag:yaml.org,2002:python/object:'+function_name, state) 
-        if not listitems and not dictitems  \ 
-                and isinstance(state, dict) and not state: 
-            return self.represent_sequence(tag+function_name, args) 
-        value = {} 
-        if args: 
-            value['args'] = args 
-        if state or not isinstance(state, dict): 
-            value['state'] = state 
-        if listitems: 
-            value['listitems'] = listitems 
-        if dictitems: 
-            value['dictitems'] = dictitems 
-        return self.represent_mapping(tag+function_name, value) 
- 
-    def represent_ordered_dict(self, data): 
-        # Provide uniform representation across different Python versions. 
-        data_type = type(data) 
-        tag = 'tag:yaml.org,2002:python/object/apply:%s.%s' \ 
-                % (data_type.__module__, data_type.__name__) 
-        items = [[key, value] for key, value in data.items()] 
-        return self.represent_sequence(tag, [items]) 
- 
-Representer.add_representer(complex, 
-        Representer.represent_complex) 
- 
-Representer.add_representer(tuple, 
-        Representer.represent_tuple) 
- 
-Representer.add_representer(type, 
-        Representer.represent_name) 
- 
-Representer.add_representer(collections.OrderedDict, 
-        Representer.represent_ordered_dict) 
- 
-Representer.add_representer(types.FunctionType, 
-        Representer.represent_name) 
- 
-Representer.add_representer(types.BuiltinFunctionType, 
-        Representer.represent_name) 
- 
-Representer.add_representer(types.ModuleType, 
-        Representer.represent_module) 
- 
-Representer.add_multi_representer(object, 
-        Representer.represent_object) 
- 
+        reduce = (list(reduce)+[None]*5)[:5]
+        function, args, state, listitems, dictitems = reduce
+        args = list(args)
+        if state is None:
+            state = {}
+        if listitems is not None:
+            listitems = list(listitems)
+        if dictitems is not None:
+            dictitems = dict(dictitems)
+        if function.__name__ == '__newobj__':
+            function = args[0]
+            args = args[1:]
+            tag = 'tag:yaml.org,2002:python/object/new:'
+            newobj = True
+        else:
+            tag = 'tag:yaml.org,2002:python/object/apply:'
+            newobj = False
+        function_name = '%s.%s' % (function.__module__, function.__name__)
+        if not args and not listitems and not dictitems \
+                and isinstance(state, dict) and newobj:
+            return self.represent_mapping(
+                    'tag:yaml.org,2002:python/object:'+function_name, state)
+        if not listitems and not dictitems  \
+                and isinstance(state, dict) and not state:
+            return self.represent_sequence(tag+function_name, args)
+        value = {}
+        if args:
+            value['args'] = args
+        if state or not isinstance(state, dict):
+            value['state'] = state
+        if listitems:
+            value['listitems'] = listitems
+        if dictitems:
+            value['dictitems'] = dictitems
+        return self.represent_mapping(tag+function_name, value)
+
+    def represent_ordered_dict(self, data):
+        # Provide uniform representation across different Python versions.
+        data_type = type(data)
+        tag = 'tag:yaml.org,2002:python/object/apply:%s.%s' \
+                % (data_type.__module__, data_type.__name__)
+        items = [[key, value] for key, value in data.items()]
+        return self.represent_sequence(tag, [items])
+
+Representer.add_representer(complex,
+        Representer.represent_complex)
+
+Representer.add_representer(tuple,
+        Representer.represent_tuple)
+
+Representer.add_representer(type,
+        Representer.represent_name)
+
+Representer.add_representer(collections.OrderedDict,
+        Representer.represent_ordered_dict)
+
+Representer.add_representer(types.FunctionType,
+        Representer.represent_name)
+
+Representer.add_representer(types.BuiltinFunctionType,
+        Representer.represent_name)
+
+Representer.add_representer(types.ModuleType,
+        Representer.represent_module)
+
+Representer.add_multi_representer(object,
+        Representer.represent_object)
+
diff --git a/contrib/python/PyYAML/py3/yaml/resolver.py b/contrib/python/PyYAML/py3/yaml/resolver.py
index 535040b1ba..013896d2f1 100644
--- a/contrib/python/PyYAML/py3/yaml/resolver.py
+++ b/contrib/python/PyYAML/py3/yaml/resolver.py
@@ -1,227 +1,227 @@
- 
-__all__ = ['BaseResolver', 'Resolver'] 
- 
-from .error import * 
-from .nodes import * 
- 
-import re 
- 
-class ResolverError(YAMLError): 
-    pass 
- 
-class BaseResolver: 
- 
-    DEFAULT_SCALAR_TAG = 'tag:yaml.org,2002:str' 
-    DEFAULT_SEQUENCE_TAG = 'tag:yaml.org,2002:seq' 
-    DEFAULT_MAPPING_TAG = 'tag:yaml.org,2002:map' 
- 
-    yaml_implicit_resolvers = {} 
-    yaml_path_resolvers = {} 
- 
-    def __init__(self): 
-        self.resolver_exact_paths = [] 
-        self.resolver_prefix_paths = [] 
- 
-    @classmethod 
-    def add_implicit_resolver(cls, tag, regexp, first): 
-        if not 'yaml_implicit_resolvers' in cls.__dict__: 
-            implicit_resolvers = {} 
-            for key in cls.yaml_implicit_resolvers: 
-                implicit_resolvers[key] = cls.yaml_implicit_resolvers[key][:] 
-            cls.yaml_implicit_resolvers = implicit_resolvers 
-        if first is None: 
-            first = [None] 
-        for ch in first: 
-            cls.yaml_implicit_resolvers.setdefault(ch, []).append((tag, regexp)) 
- 
-    @classmethod 
-    def add_path_resolver(cls, tag, path, kind=None): 
-        # Note: `add_path_resolver` is experimental.  The API could be changed. 
-        # `new_path` is a pattern that is matched against the path from the 
-        # root to the node that is being considered.  `node_path` elements are 
-        # tuples `(node_check, index_check)`.  `node_check` is a node class: 
-        # `ScalarNode`, `SequenceNode`, `MappingNode` or `None`.  `None` 
-        # matches any kind of a node.  `index_check` could be `None`, a boolean 
-        # value, a string value, or a number.  `None` and `False` match against 
-        # any _value_ of sequence and mapping nodes.  `True` matches against 
-        # any _key_ of a mapping node.  A string `index_check` matches against 
-        # a mapping value that corresponds to a scalar key which content is 
-        # equal to the `index_check` value.  An integer `index_check` matches 
-        # against a sequence value with the index equal to `index_check`. 
-        if not 'yaml_path_resolvers' in cls.__dict__: 
-            cls.yaml_path_resolvers = cls.yaml_path_resolvers.copy() 
-        new_path = [] 
-        for element in path: 
-            if isinstance(element, (list, tuple)): 
-                if len(element) == 2: 
-                    node_check, index_check = element 
-                elif len(element) == 1: 
-                    node_check = element[0] 
-                    index_check = True 
-                else: 
-                    raise ResolverError("Invalid path element: %s" % element) 
-            else: 
-                node_check = None 
-                index_check = element 
-            if node_check is str: 
-                node_check = ScalarNode 
-            elif node_check is list: 
-                node_check = SequenceNode 
-            elif node_check is dict: 
-                node_check = MappingNode 
-            elif node_check not in [ScalarNode, SequenceNode, MappingNode]  \ 
-                    and not isinstance(node_check, str) \ 
-                    and node_check is not None: 
-                raise ResolverError("Invalid node checker: %s" % node_check) 
-            if not isinstance(index_check, (str, int))  \ 
-                    and index_check is not None: 
-                raise ResolverError("Invalid index checker: %s" % index_check) 
-            new_path.append((node_check, index_check)) 
-        if kind is str: 
-            kind = ScalarNode 
-        elif kind is list: 
-            kind = SequenceNode 
-        elif kind is dict: 
-            kind = MappingNode 
-        elif kind not in [ScalarNode, SequenceNode, MappingNode]    \ 
-                and kind is not None: 
-            raise ResolverError("Invalid node kind: %s" % kind) 
-        cls.yaml_path_resolvers[tuple(new_path), kind] = tag 
- 
-    def descend_resolver(self, current_node, current_index): 
-        if not self.yaml_path_resolvers: 
-            return 
-        exact_paths = {} 
-        prefix_paths = [] 
-        if current_node: 
-            depth = len(self.resolver_prefix_paths) 
-            for path, kind in self.resolver_prefix_paths[-1]: 
-                if self.check_resolver_prefix(depth, path, kind, 
-                        current_node, current_index): 
-                    if len(path) > depth: 
-                        prefix_paths.append((path, kind)) 
-                    else: 
-                        exact_paths[kind] = self.yaml_path_resolvers[path, kind] 
-        else: 
-            for path, kind in self.yaml_path_resolvers: 
-                if not path: 
-                    exact_paths[kind] = self.yaml_path_resolvers[path, kind] 
-                else: 
-                    prefix_paths.append((path, kind)) 
-        self.resolver_exact_paths.append(exact_paths) 
-        self.resolver_prefix_paths.append(prefix_paths) 
- 
-    def ascend_resolver(self): 
-        if not self.yaml_path_resolvers: 
-            return 
-        self.resolver_exact_paths.pop() 
-        self.resolver_prefix_paths.pop() 
- 
-    def check_resolver_prefix(self, depth, path, kind, 
-            current_node, current_index): 
-        node_check, index_check = path[depth-1] 
-        if isinstance(node_check, str): 
-            if current_node.tag != node_check: 
-                return 
-        elif node_check is not None: 
-            if not isinstance(current_node, node_check): 
-                return 
-        if index_check is True and current_index is not None: 
-            return 
-        if (index_check is False or index_check is None)    \ 
-                and current_index is None: 
-            return 
-        if isinstance(index_check, str): 
-            if not (isinstance(current_index, ScalarNode) 
-                    and index_check == current_index.value): 
-                return 
-        elif isinstance(index_check, int) and not isinstance(index_check, bool): 
-            if index_check != current_index: 
-                return 
-        return True 
- 
-    def resolve(self, kind, value, implicit): 
-        if kind is ScalarNode and implicit[0]: 
-            if value == '': 
-                resolvers = self.yaml_implicit_resolvers.get('', []) 
-            else: 
-                resolvers = self.yaml_implicit_resolvers.get(value[0], []) 
+
+__all__ = ['BaseResolver', 'Resolver']
+
+from .error import *
+from .nodes import *
+
+import re
+
+class ResolverError(YAMLError):
+    pass
+
+class BaseResolver:
+
+    DEFAULT_SCALAR_TAG = 'tag:yaml.org,2002:str'
+    DEFAULT_SEQUENCE_TAG = 'tag:yaml.org,2002:seq'
+    DEFAULT_MAPPING_TAG = 'tag:yaml.org,2002:map'
+
+    yaml_implicit_resolvers = {}
+    yaml_path_resolvers = {}
+
+    def __init__(self):
+        self.resolver_exact_paths = []
+        self.resolver_prefix_paths = []
+
+    @classmethod
+    def add_implicit_resolver(cls, tag, regexp, first):
+        if not 'yaml_implicit_resolvers' in cls.__dict__:
+            implicit_resolvers = {}
+            for key in cls.yaml_implicit_resolvers:
+                implicit_resolvers[key] = cls.yaml_implicit_resolvers[key][:]
+            cls.yaml_implicit_resolvers = implicit_resolvers
+        if first is None:
+            first = [None]
+        for ch in first:
+            cls.yaml_implicit_resolvers.setdefault(ch, []).append((tag, regexp))
+
+    @classmethod
+    def add_path_resolver(cls, tag, path, kind=None):
+        # Note: `add_path_resolver` is experimental.  The API could be changed.
+        # `new_path` is a pattern that is matched against the path from the
+        # root to the node that is being considered.  `node_path` elements are
+        # tuples `(node_check, index_check)`.  `node_check` is a node class:
+        # `ScalarNode`, `SequenceNode`, `MappingNode` or `None`.  `None`
+        # matches any kind of a node.  `index_check` could be `None`, a boolean
+        # value, a string value, or a number.  `None` and `False` match against
+        # any _value_ of sequence and mapping nodes.  `True` matches against
+        # any _key_ of a mapping node.  A string `index_check` matches against
+        # a mapping value that corresponds to a scalar key which content is
+        # equal to the `index_check` value.  An integer `index_check` matches
+        # against a sequence value with the index equal to `index_check`.
+        if not 'yaml_path_resolvers' in cls.__dict__:
+            cls.yaml_path_resolvers = cls.yaml_path_resolvers.copy()
+        new_path = []
+        for element in path:
+            if isinstance(element, (list, tuple)):
+                if len(element) == 2:
+                    node_check, index_check = element
+                elif len(element) == 1:
+                    node_check = element[0]
+                    index_check = True
+                else:
+                    raise ResolverError("Invalid path element: %s" % element)
+            else:
+                node_check = None
+                index_check = element
+            if node_check is str:
+                node_check = ScalarNode
+            elif node_check is list:
+                node_check = SequenceNode
+            elif node_check is dict:
+                node_check = MappingNode
+            elif node_check not in [ScalarNode, SequenceNode, MappingNode]  \
+                    and not isinstance(node_check, str) \
+                    and node_check is not None:
+                raise ResolverError("Invalid node checker: %s" % node_check)
+            if not isinstance(index_check, (str, int))  \
+                    and index_check is not None:
+                raise ResolverError("Invalid index checker: %s" % index_check)
+            new_path.append((node_check, index_check))
+        if kind is str:
+            kind = ScalarNode
+        elif kind is list:
+            kind = SequenceNode
+        elif kind is dict:
+            kind = MappingNode
+        elif kind not in [ScalarNode, SequenceNode, MappingNode]    \
+                and kind is not None:
+            raise ResolverError("Invalid node kind: %s" % kind)
+        cls.yaml_path_resolvers[tuple(new_path), kind] = tag
+
+    def descend_resolver(self, current_node, current_index):
+        if not self.yaml_path_resolvers:
+            return
+        exact_paths = {}
+        prefix_paths = []
+        if current_node:
+            depth = len(self.resolver_prefix_paths)
+            for path, kind in self.resolver_prefix_paths[-1]:
+                if self.check_resolver_prefix(depth, path, kind,
+                        current_node, current_index):
+                    if len(path) > depth:
+                        prefix_paths.append((path, kind))
+                    else:
+                        exact_paths[kind] = self.yaml_path_resolvers[path, kind]
+        else:
+            for path, kind in self.yaml_path_resolvers:
+                if not path:
+                    exact_paths[kind] = self.yaml_path_resolvers[path, kind]
+                else:
+                    prefix_paths.append((path, kind))
+        self.resolver_exact_paths.append(exact_paths)
+        self.resolver_prefix_paths.append(prefix_paths)
+
+    def ascend_resolver(self):
+        if not self.yaml_path_resolvers:
+            return
+        self.resolver_exact_paths.pop()
+        self.resolver_prefix_paths.pop()
+
+    def check_resolver_prefix(self, depth, path, kind,
+            current_node, current_index):
+        node_check, index_check = path[depth-1]
+        if isinstance(node_check, str):
+            if current_node.tag != node_check:
+                return
+        elif node_check is not None:
+            if not isinstance(current_node, node_check):
+                return
+        if index_check is True and current_index is not None:
+            return
+        if (index_check is False or index_check is None)    \
+                and current_index is None:
+            return
+        if isinstance(index_check, str):
+            if not (isinstance(current_index, ScalarNode)
+                    and index_check == current_index.value):
+                return
+        elif isinstance(index_check, int) and not isinstance(index_check, bool):
+            if index_check != current_index:
+                return
+        return True
+
+    def resolve(self, kind, value, implicit):
+        if kind is ScalarNode and implicit[0]:
+            if value == '':
+                resolvers = self.yaml_implicit_resolvers.get('', [])
+            else:
+                resolvers = self.yaml_implicit_resolvers.get(value[0], [])
             wildcard_resolvers = self.yaml_implicit_resolvers.get(None, [])
             for tag, regexp in resolvers + wildcard_resolvers:
-                if regexp.match(value): 
-                    return tag 
-            implicit = implicit[1] 
-        if self.yaml_path_resolvers: 
-            exact_paths = self.resolver_exact_paths[-1] 
-            if kind in exact_paths: 
-                return exact_paths[kind] 
-            if None in exact_paths: 
-                return exact_paths[None] 
-        if kind is ScalarNode: 
-            return self.DEFAULT_SCALAR_TAG 
-        elif kind is SequenceNode: 
-            return self.DEFAULT_SEQUENCE_TAG 
-        elif kind is MappingNode: 
-            return self.DEFAULT_MAPPING_TAG 
- 
-class Resolver(BaseResolver): 
-    pass 
- 
-Resolver.add_implicit_resolver( 
-        'tag:yaml.org,2002:bool', 
-        re.compile(r'''^(?:yes|Yes|YES|no|No|NO 
-                    |true|True|TRUE|false|False|FALSE 
-                    |on|On|ON|off|Off|OFF)$''', re.X), 
-        list('yYnNtTfFoO')) 
- 
-Resolver.add_implicit_resolver( 
-        'tag:yaml.org,2002:float', 
-        re.compile(r'''^(?:[-+]?(?:[0-9][0-9_]*)\.[0-9_]*(?:[eE][-+][0-9]+)? 
-                    |\.[0-9_]+(?:[eE][-+][0-9]+)? 
-                    |[-+]?[0-9][0-9_]*(?::[0-5]?[0-9])+\.[0-9_]* 
-                    |[-+]?\.(?:inf|Inf|INF) 
-                    |\.(?:nan|NaN|NAN))$''', re.X), 
-        list('-+0123456789.')) 
- 
-Resolver.add_implicit_resolver( 
-        'tag:yaml.org,2002:int', 
-        re.compile(r'''^(?:[-+]?0b[0-1_]+ 
-                    |[-+]?0[0-7_]+ 
-                    |[-+]?(?:0|[1-9][0-9_]*) 
-                    |[-+]?0x[0-9a-fA-F_]+ 
-                    |[-+]?[1-9][0-9_]*(?::[0-5]?[0-9])+)$''', re.X), 
-        list('-+0123456789')) 
- 
-Resolver.add_implicit_resolver( 
-        'tag:yaml.org,2002:merge', 
-        re.compile(r'^(?:<<)$'), 
-        ['<']) 
- 
-Resolver.add_implicit_resolver( 
-        'tag:yaml.org,2002:null', 
-        re.compile(r'''^(?: ~ 
-                    |null|Null|NULL 
-                    | )$''', re.X), 
-        ['~', 'n', 'N', '']) 
- 
-Resolver.add_implicit_resolver( 
-        'tag:yaml.org,2002:timestamp', 
-        re.compile(r'''^(?:[0-9][0-9][0-9][0-9]-[0-9][0-9]-[0-9][0-9] 
-                    |[0-9][0-9][0-9][0-9] -[0-9][0-9]? -[0-9][0-9]? 
-                     (?:[Tt]|[ \t]+)[0-9][0-9]? 
-                     :[0-9][0-9] :[0-9][0-9] (?:\.[0-9]*)? 
-                     (?:[ \t]*(?:Z|[-+][0-9][0-9]?(?::[0-9][0-9])?))?)$''', re.X), 
-        list('0123456789')) 
- 
-Resolver.add_implicit_resolver( 
-        'tag:yaml.org,2002:value', 
-        re.compile(r'^(?:=)$'), 
-        ['=']) 
- 
-# The following resolver is only for documentation purposes. It cannot work 
-# because plain scalars cannot start with '!', '&', or '*'. 
-Resolver.add_implicit_resolver( 
-        'tag:yaml.org,2002:yaml', 
-        re.compile(r'^(?:!|&|\*)$'), 
-        list('!&*')) 
- 
+                if regexp.match(value):
+                    return tag
+            implicit = implicit[1]
+        if self.yaml_path_resolvers:
+            exact_paths = self.resolver_exact_paths[-1]
+            if kind in exact_paths:
+                return exact_paths[kind]
+            if None in exact_paths:
+                return exact_paths[None]
+        if kind is ScalarNode:
+            return self.DEFAULT_SCALAR_TAG
+        elif kind is SequenceNode:
+            return self.DEFAULT_SEQUENCE_TAG
+        elif kind is MappingNode:
+            return self.DEFAULT_MAPPING_TAG
+
+class Resolver(BaseResolver):
+    pass
+
+Resolver.add_implicit_resolver(
+        'tag:yaml.org,2002:bool',
+        re.compile(r'''^(?:yes|Yes|YES|no|No|NO
+                    |true|True|TRUE|false|False|FALSE
+                    |on|On|ON|off|Off|OFF)$''', re.X),
+        list('yYnNtTfFoO'))
+
+Resolver.add_implicit_resolver(
+        'tag:yaml.org,2002:float',
+        re.compile(r'''^(?:[-+]?(?:[0-9][0-9_]*)\.[0-9_]*(?:[eE][-+][0-9]+)?
+                    |\.[0-9_]+(?:[eE][-+][0-9]+)?
+                    |[-+]?[0-9][0-9_]*(?::[0-5]?[0-9])+\.[0-9_]*
+                    |[-+]?\.(?:inf|Inf|INF)
+                    |\.(?:nan|NaN|NAN))$''', re.X),
+        list('-+0123456789.'))
+
+Resolver.add_implicit_resolver(
+        'tag:yaml.org,2002:int',
+        re.compile(r'''^(?:[-+]?0b[0-1_]+
+                    |[-+]?0[0-7_]+
+                    |[-+]?(?:0|[1-9][0-9_]*)
+                    |[-+]?0x[0-9a-fA-F_]+
+                    |[-+]?[1-9][0-9_]*(?::[0-5]?[0-9])+)$''', re.X),
+        list('-+0123456789'))
+
+Resolver.add_implicit_resolver(
+        'tag:yaml.org,2002:merge',
+        re.compile(r'^(?:<<)$'),
+        ['<'])
+
+Resolver.add_implicit_resolver(
+        'tag:yaml.org,2002:null',
+        re.compile(r'''^(?: ~
+                    |null|Null|NULL
+                    | )$''', re.X),
+        ['~', 'n', 'N', ''])
+
+Resolver.add_implicit_resolver(
+        'tag:yaml.org,2002:timestamp',
+        re.compile(r'''^(?:[0-9][0-9][0-9][0-9]-[0-9][0-9]-[0-9][0-9]
+                    |[0-9][0-9][0-9][0-9] -[0-9][0-9]? -[0-9][0-9]?
+                     (?:[Tt]|[ \t]+)[0-9][0-9]?
+                     :[0-9][0-9] :[0-9][0-9] (?:\.[0-9]*)?
+                     (?:[ \t]*(?:Z|[-+][0-9][0-9]?(?::[0-9][0-9])?))?)$''', re.X),
+        list('0123456789'))
+
+Resolver.add_implicit_resolver(
+        'tag:yaml.org,2002:value',
+        re.compile(r'^(?:=)$'),
+        ['='])
+
+# The following resolver is only for documentation purposes. It cannot work
+# because plain scalars cannot start with '!', '&', or '*'.
+Resolver.add_implicit_resolver(
+        'tag:yaml.org,2002:yaml',
+        re.compile(r'^(?:!|&|\*)$'),
+        list('!&*'))
+
diff --git a/contrib/python/PyYAML/py3/yaml/scanner.py b/contrib/python/PyYAML/py3/yaml/scanner.py
index a1268e8f2b..7437ede1c6 100644
--- a/contrib/python/PyYAML/py3/yaml/scanner.py
+++ b/contrib/python/PyYAML/py3/yaml/scanner.py
@@ -1,1435 +1,1435 @@
- 
-# Scanner produces tokens of the following types: 
-# STREAM-START 
-# STREAM-END 
-# DIRECTIVE(name, value) 
-# DOCUMENT-START 
-# DOCUMENT-END 
-# BLOCK-SEQUENCE-START 
-# BLOCK-MAPPING-START 
-# BLOCK-END 
-# FLOW-SEQUENCE-START 
-# FLOW-MAPPING-START 
-# FLOW-SEQUENCE-END 
-# FLOW-MAPPING-END 
-# BLOCK-ENTRY 
-# FLOW-ENTRY 
-# KEY 
-# VALUE 
-# ALIAS(value) 
-# ANCHOR(value) 
-# TAG(value) 
-# SCALAR(value, plain, style) 
-# 
-# Read comments in the Scanner code for more details. 
-# 
- 
-__all__ = ['Scanner', 'ScannerError'] 
- 
-from .error import MarkedYAMLError 
-from .tokens import * 
- 
-class ScannerError(MarkedYAMLError): 
-    pass 
- 
-class SimpleKey: 
-    # See below simple keys treatment. 
- 
-    def __init__(self, token_number, required, index, line, column, mark): 
-        self.token_number = token_number 
-        self.required = required 
-        self.index = index 
-        self.line = line 
-        self.column = column 
-        self.mark = mark 
- 
-class Scanner: 
- 
-    def __init__(self): 
-        """Initialize the scanner.""" 
-        # It is assumed that Scanner and Reader will have a common descendant. 
-        # Reader do the dirty work of checking for BOM and converting the 
-        # input data to Unicode. It also adds NUL to the end. 
-        # 
-        # Reader supports the following methods 
-        #   self.peek(i=0)       # peek the next i-th character 
-        #   self.prefix(l=1)     # peek the next l characters 
-        #   self.forward(l=1)    # read the next l characters and move the pointer. 
- 
-        # Had we reached the end of the stream? 
-        self.done = False 
- 
-        # The number of unclosed '{' and '['. `flow_level == 0` means block 
-        # context. 
-        self.flow_level = 0 
- 
-        # List of processed tokens that are not yet emitted. 
-        self.tokens = [] 
- 
-        # Add the STREAM-START token. 
-        self.fetch_stream_start() 
- 
-        # Number of tokens that were emitted through the `get_token` method. 
-        self.tokens_taken = 0 
- 
-        # The current indentation level. 
-        self.indent = -1 
- 
-        # Past indentation levels. 
-        self.indents = [] 
- 
-        # Variables related to simple keys treatment. 
- 
-        # A simple key is a key that is not denoted by the '?' indicator. 
-        # Example of simple keys: 
-        #   --- 
-        #   block simple key: value 
-        #   ? not a simple key: 
-        #   : { flow simple key: value } 
-        # We emit the KEY token before all keys, so when we find a potential 
-        # simple key, we try to locate the corresponding ':' indicator. 
-        # Simple keys should be limited to a single line and 1024 characters. 
- 
-        # Can a simple key start at the current position? A simple key may 
-        # start: 
-        # - at the beginning of the line, not counting indentation spaces 
-        #       (in block context), 
-        # - after '{', '[', ',' (in the flow context), 
-        # - after '?', ':', '-' (in the block context). 
-        # In the block context, this flag also signifies if a block collection 
-        # may start at the current position. 
-        self.allow_simple_key = True 
- 
-        # Keep track of possible simple keys. This is a dictionary. The key 
-        # is `flow_level`; there can be no more that one possible simple key 
-        # for each level. The value is a SimpleKey record: 
-        #   (token_number, required, index, line, column, mark) 
-        # A simple key may start with ALIAS, ANCHOR, TAG, SCALAR(flow), 
-        # '[', or '{' tokens. 
-        self.possible_simple_keys = {} 
- 
-    # Public methods. 
- 
-    def check_token(self, *choices): 
-        # Check if the next token is one of the given types. 
-        while self.need_more_tokens(): 
-            self.fetch_more_tokens() 
-        if self.tokens: 
-            if not choices: 
-                return True 
-            for choice in choices: 
-                if isinstance(self.tokens[0], choice): 
-                    return True 
-        return False 
- 
-    def peek_token(self): 
-        # Return the next token, but do not delete if from the queue. 
+
+# Scanner produces tokens of the following types:
+# STREAM-START
+# STREAM-END
+# DIRECTIVE(name, value)
+# DOCUMENT-START
+# DOCUMENT-END
+# BLOCK-SEQUENCE-START
+# BLOCK-MAPPING-START
+# BLOCK-END
+# FLOW-SEQUENCE-START
+# FLOW-MAPPING-START
+# FLOW-SEQUENCE-END
+# FLOW-MAPPING-END
+# BLOCK-ENTRY
+# FLOW-ENTRY
+# KEY
+# VALUE
+# ALIAS(value)
+# ANCHOR(value)
+# TAG(value)
+# SCALAR(value, plain, style)
+#
+# Read comments in the Scanner code for more details.
+#
+
+__all__ = ['Scanner', 'ScannerError']
+
+from .error import MarkedYAMLError
+from .tokens import *
+
+class ScannerError(MarkedYAMLError):
+    pass
+
+class SimpleKey:
+    # See below simple keys treatment.
+
+    def __init__(self, token_number, required, index, line, column, mark):
+        self.token_number = token_number
+        self.required = required
+        self.index = index
+        self.line = line
+        self.column = column
+        self.mark = mark
+
+class Scanner:
+
+    def __init__(self):
+        """Initialize the scanner."""
+        # It is assumed that Scanner and Reader will have a common descendant.
+        # Reader do the dirty work of checking for BOM and converting the
+        # input data to Unicode. It also adds NUL to the end.
+        #
+        # Reader supports the following methods
+        #   self.peek(i=0)       # peek the next i-th character
+        #   self.prefix(l=1)     # peek the next l characters
+        #   self.forward(l=1)    # read the next l characters and move the pointer.
+
+        # Had we reached the end of the stream?
+        self.done = False
+
+        # The number of unclosed '{' and '['. `flow_level == 0` means block
+        # context.
+        self.flow_level = 0
+
+        # List of processed tokens that are not yet emitted.
+        self.tokens = []
+
+        # Add the STREAM-START token.
+        self.fetch_stream_start()
+
+        # Number of tokens that were emitted through the `get_token` method.
+        self.tokens_taken = 0
+
+        # The current indentation level.
+        self.indent = -1
+
+        # Past indentation levels.
+        self.indents = []
+
+        # Variables related to simple keys treatment.
+
+        # A simple key is a key that is not denoted by the '?' indicator.
+        # Example of simple keys:
+        #   ---
+        #   block simple key: value
+        #   ? not a simple key:
+        #   : { flow simple key: value }
+        # We emit the KEY token before all keys, so when we find a potential
+        # simple key, we try to locate the corresponding ':' indicator.
+        # Simple keys should be limited to a single line and 1024 characters.
+
+        # Can a simple key start at the current position? A simple key may
+        # start:
+        # - at the beginning of the line, not counting indentation spaces
+        #       (in block context),
+        # - after '{', '[', ',' (in the flow context),
+        # - after '?', ':', '-' (in the block context).
+        # In the block context, this flag also signifies if a block collection
+        # may start at the current position.
+        self.allow_simple_key = True
+
+        # Keep track of possible simple keys. This is a dictionary. The key
+        # is `flow_level`; there can be no more that one possible simple key
+        # for each level. The value is a SimpleKey record:
+        #   (token_number, required, index, line, column, mark)
+        # A simple key may start with ALIAS, ANCHOR, TAG, SCALAR(flow),
+        # '[', or '{' tokens.
+        self.possible_simple_keys = {}
+
+    # Public methods.
+
+    def check_token(self, *choices):
+        # Check if the next token is one of the given types.
+        while self.need_more_tokens():
+            self.fetch_more_tokens()
+        if self.tokens:
+            if not choices:
+                return True
+            for choice in choices:
+                if isinstance(self.tokens[0], choice):
+                    return True
+        return False
+
+    def peek_token(self):
+        # Return the next token, but do not delete if from the queue.
         # Return None if no more tokens.
-        while self.need_more_tokens(): 
-            self.fetch_more_tokens() 
-        if self.tokens: 
-            return self.tokens[0] 
+        while self.need_more_tokens():
+            self.fetch_more_tokens()
+        if self.tokens:
+            return self.tokens[0]
         else:
             return None
- 
-    def get_token(self): 
-        # Return the next token. 
-        while self.need_more_tokens(): 
-            self.fetch_more_tokens() 
-        if self.tokens: 
-            self.tokens_taken += 1 
-            return self.tokens.pop(0) 
- 
-    # Private methods. 
- 
-    def need_more_tokens(self): 
-        if self.done: 
-            return False 
-        if not self.tokens: 
-            return True 
-        # The current token may be a potential simple key, so we 
-        # need to look further. 
-        self.stale_possible_simple_keys() 
-        if self.next_possible_simple_key() == self.tokens_taken: 
-            return True 
- 
-    def fetch_more_tokens(self): 
- 
-        # Eat whitespaces and comments until we reach the next token. 
-        self.scan_to_next_token() 
- 
-        # Remove obsolete possible simple keys. 
-        self.stale_possible_simple_keys() 
- 
-        # Compare the current indentation and column. It may add some tokens 
-        # and decrease the current indentation level. 
-        self.unwind_indent(self.column) 
- 
-        # Peek the next character. 
-        ch = self.peek() 
- 
-        # Is it the end of stream? 
-        if ch == '\0': 
-            return self.fetch_stream_end() 
- 
-        # Is it a directive? 
-        if ch == '%' and self.check_directive(): 
-            return self.fetch_directive() 
- 
-        # Is it the document start? 
-        if ch == '-' and self.check_document_start(): 
-            return self.fetch_document_start() 
- 
-        # Is it the document end? 
-        if ch == '.' and self.check_document_end(): 
-            return self.fetch_document_end() 
- 
-        # TODO: support for BOM within a stream. 
-        #if ch == '\uFEFF': 
-        #    return self.fetch_bom()    <-- issue BOMToken 
- 
-        # Note: the order of the following checks is NOT significant. 
- 
-        # Is it the flow sequence start indicator? 
-        if ch == '[': 
-            return self.fetch_flow_sequence_start() 
- 
-        # Is it the flow mapping start indicator? 
-        if ch == '{': 
-            return self.fetch_flow_mapping_start() 
- 
-        # Is it the flow sequence end indicator? 
-        if ch == ']': 
-            return self.fetch_flow_sequence_end() 
- 
-        # Is it the flow mapping end indicator? 
-        if ch == '}': 
-            return self.fetch_flow_mapping_end() 
- 
-        # Is it the flow entry indicator? 
-        if ch == ',': 
-            return self.fetch_flow_entry() 
- 
-        # Is it the block entry indicator? 
-        if ch == '-' and self.check_block_entry(): 
-            return self.fetch_block_entry() 
- 
-        # Is it the key indicator? 
-        if ch == '?' and self.check_key(): 
-            return self.fetch_key() 
- 
-        # Is it the value indicator? 
-        if ch == ':' and self.check_value(): 
-            return self.fetch_value() 
- 
-        # Is it an alias? 
-        if ch == '*': 
-            return self.fetch_alias() 
- 
-        # Is it an anchor? 
-        if ch == '&': 
-            return self.fetch_anchor() 
- 
-        # Is it a tag? 
-        if ch == '!': 
-            return self.fetch_tag() 
- 
-        # Is it a literal scalar? 
-        if ch == '|' and not self.flow_level: 
-            return self.fetch_literal() 
- 
-        # Is it a folded scalar? 
-        if ch == '>' and not self.flow_level: 
-            return self.fetch_folded() 
- 
-        # Is it a single quoted scalar? 
-        if ch == '\'': 
-            return self.fetch_single() 
- 
-        # Is it a double quoted scalar? 
-        if ch == '\"': 
-            return self.fetch_double() 
- 
-        # It must be a plain scalar then. 
-        if self.check_plain(): 
-            return self.fetch_plain() 
- 
-        # No? It's an error. Let's produce a nice error message. 
-        raise ScannerError("while scanning for the next token", None, 
-                "found character %r that cannot start any token" % ch, 
-                self.get_mark()) 
- 
-    # Simple keys treatment. 
- 
-    def next_possible_simple_key(self): 
-        # Return the number of the nearest possible simple key. Actually we 
-        # don't need to loop through the whole dictionary. We may replace it 
-        # with the following code: 
-        #   if not self.possible_simple_keys: 
-        #       return None 
-        #   return self.possible_simple_keys[ 
-        #           min(self.possible_simple_keys.keys())].token_number 
-        min_token_number = None 
-        for level in self.possible_simple_keys: 
-            key = self.possible_simple_keys[level] 
-            if min_token_number is None or key.token_number < min_token_number: 
-                min_token_number = key.token_number 
-        return min_token_number 
- 
-    def stale_possible_simple_keys(self): 
-        # Remove entries that are no longer possible simple keys. According to 
-        # the YAML specification, simple keys 
-        # - should be limited to a single line, 
-        # - should be no longer than 1024 characters. 
-        # Disabling this procedure will allow simple keys of any length and 
-        # height (may cause problems if indentation is broken though). 
-        for level in list(self.possible_simple_keys): 
-            key = self.possible_simple_keys[level] 
-            if key.line != self.line  \ 
-                    or self.index-key.index > 1024: 
-                if key.required: 
-                    raise ScannerError("while scanning a simple key", key.mark, 
-                            "could not find expected ':'", self.get_mark()) 
-                del self.possible_simple_keys[level] 
- 
-    def save_possible_simple_key(self): 
-        # The next token may start a simple key. We check if it's possible 
-        # and save its position. This function is called for 
-        #   ALIAS, ANCHOR, TAG, SCALAR(flow), '[', and '{'. 
- 
-        # Check if a simple key is required at the current position. 
-        required = not self.flow_level and self.indent == self.column 
- 
-        # The next token might be a simple key. Let's save it's number and 
-        # position. 
-        if self.allow_simple_key: 
-            self.remove_possible_simple_key() 
-            token_number = self.tokens_taken+len(self.tokens) 
-            key = SimpleKey(token_number, required, 
-                    self.index, self.line, self.column, self.get_mark()) 
-            self.possible_simple_keys[self.flow_level] = key 
- 
-    def remove_possible_simple_key(self): 
-        # Remove the saved possible key position at the current flow level. 
-        if self.flow_level in self.possible_simple_keys: 
-            key = self.possible_simple_keys[self.flow_level] 
-             
-            if key.required: 
-                raise ScannerError("while scanning a simple key", key.mark, 
-                        "could not find expected ':'", self.get_mark()) 
- 
-            del self.possible_simple_keys[self.flow_level] 
- 
-    # Indentation functions. 
- 
-    def unwind_indent(self, column): 
- 
-        ## In flow context, tokens should respect indentation. 
-        ## Actually the condition should be `self.indent >= column` according to 
-        ## the spec. But this condition will prohibit intuitively correct 
-        ## constructions such as 
-        ## key : { 
-        ## } 
-        #if self.flow_level and self.indent > column: 
-        #    raise ScannerError(None, None, 
+
+    def get_token(self):
+        # Return the next token.
+        while self.need_more_tokens():
+            self.fetch_more_tokens()
+        if self.tokens:
+            self.tokens_taken += 1
+            return self.tokens.pop(0)
+
+    # Private methods.
+
+    def need_more_tokens(self):
+        if self.done:
+            return False
+        if not self.tokens:
+            return True
+        # The current token may be a potential simple key, so we
+        # need to look further.
+        self.stale_possible_simple_keys()
+        if self.next_possible_simple_key() == self.tokens_taken:
+            return True
+
+    def fetch_more_tokens(self):
+
+        # Eat whitespaces and comments until we reach the next token.
+        self.scan_to_next_token()
+
+        # Remove obsolete possible simple keys.
+        self.stale_possible_simple_keys()
+
+        # Compare the current indentation and column. It may add some tokens
+        # and decrease the current indentation level.
+        self.unwind_indent(self.column)
+
+        # Peek the next character.
+        ch = self.peek()
+
+        # Is it the end of stream?
+        if ch == '\0':
+            return self.fetch_stream_end()
+
+        # Is it a directive?
+        if ch == '%' and self.check_directive():
+            return self.fetch_directive()
+
+        # Is it the document start?
+        if ch == '-' and self.check_document_start():
+            return self.fetch_document_start()
+
+        # Is it the document end?
+        if ch == '.' and self.check_document_end():
+            return self.fetch_document_end()
+
+        # TODO: support for BOM within a stream.
+        #if ch == '\uFEFF':
+        #    return self.fetch_bom()    <-- issue BOMToken
+
+        # Note: the order of the following checks is NOT significant.
+
+        # Is it the flow sequence start indicator?
+        if ch == '[':
+            return self.fetch_flow_sequence_start()
+
+        # Is it the flow mapping start indicator?
+        if ch == '{':
+            return self.fetch_flow_mapping_start()
+
+        # Is it the flow sequence end indicator?
+        if ch == ']':
+            return self.fetch_flow_sequence_end()
+
+        # Is it the flow mapping end indicator?
+        if ch == '}':
+            return self.fetch_flow_mapping_end()
+
+        # Is it the flow entry indicator?
+        if ch == ',':
+            return self.fetch_flow_entry()
+
+        # Is it the block entry indicator?
+        if ch == '-' and self.check_block_entry():
+            return self.fetch_block_entry()
+
+        # Is it the key indicator?
+        if ch == '?' and self.check_key():
+            return self.fetch_key()
+
+        # Is it the value indicator?
+        if ch == ':' and self.check_value():
+            return self.fetch_value()
+
+        # Is it an alias?
+        if ch == '*':
+            return self.fetch_alias()
+
+        # Is it an anchor?
+        if ch == '&':
+            return self.fetch_anchor()
+
+        # Is it a tag?
+        if ch == '!':
+            return self.fetch_tag()
+
+        # Is it a literal scalar?
+        if ch == '|' and not self.flow_level:
+            return self.fetch_literal()
+
+        # Is it a folded scalar?
+        if ch == '>' and not self.flow_level:
+            return self.fetch_folded()
+
+        # Is it a single quoted scalar?
+        if ch == '\'':
+            return self.fetch_single()
+
+        # Is it a double quoted scalar?
+        if ch == '\"':
+            return self.fetch_double()
+
+        # It must be a plain scalar then.
+        if self.check_plain():
+            return self.fetch_plain()
+
+        # No? It's an error. Let's produce a nice error message.
+        raise ScannerError("while scanning for the next token", None,
+                "found character %r that cannot start any token" % ch,
+                self.get_mark())
+
+    # Simple keys treatment.
+
+    def next_possible_simple_key(self):
+        # Return the number of the nearest possible simple key. Actually we
+        # don't need to loop through the whole dictionary. We may replace it
+        # with the following code:
+        #   if not self.possible_simple_keys:
+        #       return None
+        #   return self.possible_simple_keys[
+        #           min(self.possible_simple_keys.keys())].token_number
+        min_token_number = None
+        for level in self.possible_simple_keys:
+            key = self.possible_simple_keys[level]
+            if min_token_number is None or key.token_number < min_token_number:
+                min_token_number = key.token_number
+        return min_token_number
+
+    def stale_possible_simple_keys(self):
+        # Remove entries that are no longer possible simple keys. According to
+        # the YAML specification, simple keys
+        # - should be limited to a single line,
+        # - should be no longer than 1024 characters.
+        # Disabling this procedure will allow simple keys of any length and
+        # height (may cause problems if indentation is broken though).
+        for level in list(self.possible_simple_keys):
+            key = self.possible_simple_keys[level]
+            if key.line != self.line  \
+                    or self.index-key.index > 1024:
+                if key.required:
+                    raise ScannerError("while scanning a simple key", key.mark,
+                            "could not find expected ':'", self.get_mark())
+                del self.possible_simple_keys[level]
+
+    def save_possible_simple_key(self):
+        # The next token may start a simple key. We check if it's possible
+        # and save its position. This function is called for
+        #   ALIAS, ANCHOR, TAG, SCALAR(flow), '[', and '{'.
+
+        # Check if a simple key is required at the current position.
+        required = not self.flow_level and self.indent == self.column
+
+        # The next token might be a simple key. Let's save it's number and
+        # position.
+        if self.allow_simple_key:
+            self.remove_possible_simple_key()
+            token_number = self.tokens_taken+len(self.tokens)
+            key = SimpleKey(token_number, required,
+                    self.index, self.line, self.column, self.get_mark())
+            self.possible_simple_keys[self.flow_level] = key
+
+    def remove_possible_simple_key(self):
+        # Remove the saved possible key position at the current flow level.
+        if self.flow_level in self.possible_simple_keys:
+            key = self.possible_simple_keys[self.flow_level]
+            
+            if key.required:
+                raise ScannerError("while scanning a simple key", key.mark,
+                        "could not find expected ':'", self.get_mark())
+
+            del self.possible_simple_keys[self.flow_level]
+
+    # Indentation functions.
+
+    def unwind_indent(self, column):
+
+        ## In flow context, tokens should respect indentation.
+        ## Actually the condition should be `self.indent >= column` according to
+        ## the spec. But this condition will prohibit intuitively correct
+        ## constructions such as
+        ## key : {
+        ## }
+        #if self.flow_level and self.indent > column:
+        #    raise ScannerError(None, None,
         #            "invalid indentation or unclosed '[' or '{'",
-        #            self.get_mark()) 
- 
-        # In the flow context, indentation is ignored. We make the scanner less 
-        # restrictive then specification requires. 
-        if self.flow_level: 
-            return 
- 
-        # In block context, we may need to issue the BLOCK-END tokens. 
-        while self.indent > column: 
-            mark = self.get_mark() 
-            self.indent = self.indents.pop() 
-            self.tokens.append(BlockEndToken(mark, mark)) 
- 
-    def add_indent(self, column): 
-        # Check if we need to increase indentation. 
-        if self.indent < column: 
-            self.indents.append(self.indent) 
-            self.indent = column 
-            return True 
-        return False 
- 
-    # Fetchers. 
- 
-    def fetch_stream_start(self): 
-        # We always add STREAM-START as the first token and STREAM-END as the 
-        # last token. 
- 
-        # Read the token. 
-        mark = self.get_mark() 
-         
-        # Add STREAM-START. 
-        self.tokens.append(StreamStartToken(mark, mark, 
-            encoding=self.encoding)) 
-         
- 
-    def fetch_stream_end(self): 
- 
+        #            self.get_mark())
+
+        # In the flow context, indentation is ignored. We make the scanner less
+        # restrictive then specification requires.
+        if self.flow_level:
+            return
+
+        # In block context, we may need to issue the BLOCK-END tokens.
+        while self.indent > column:
+            mark = self.get_mark()
+            self.indent = self.indents.pop()
+            self.tokens.append(BlockEndToken(mark, mark))
+
+    def add_indent(self, column):
+        # Check if we need to increase indentation.
+        if self.indent < column:
+            self.indents.append(self.indent)
+            self.indent = column
+            return True
+        return False
+
+    # Fetchers.
+
+    def fetch_stream_start(self):
+        # We always add STREAM-START as the first token and STREAM-END as the
+        # last token.
+
+        # Read the token.
+        mark = self.get_mark()
+        
+        # Add STREAM-START.
+        self.tokens.append(StreamStartToken(mark, mark,
+            encoding=self.encoding))
+        
+
+    def fetch_stream_end(self):
+
         # Set the current indentation to -1.
-        self.unwind_indent(-1) 
- 
-        # Reset simple keys. 
-        self.remove_possible_simple_key() 
-        self.allow_simple_key = False 
-        self.possible_simple_keys = {} 
- 
-        # Read the token. 
-        mark = self.get_mark() 
-         
-        # Add STREAM-END. 
-        self.tokens.append(StreamEndToken(mark, mark)) 
- 
-        # The steam is finished. 
-        self.done = True 
- 
-    def fetch_directive(self): 
-         
+        self.unwind_indent(-1)
+
+        # Reset simple keys.
+        self.remove_possible_simple_key()
+        self.allow_simple_key = False
+        self.possible_simple_keys = {}
+
+        # Read the token.
+        mark = self.get_mark()
+        
+        # Add STREAM-END.
+        self.tokens.append(StreamEndToken(mark, mark))
+
+        # The steam is finished.
+        self.done = True
+
+    def fetch_directive(self):
+        
         # Set the current indentation to -1.
-        self.unwind_indent(-1) 
- 
-        # Reset simple keys. 
-        self.remove_possible_simple_key() 
-        self.allow_simple_key = False 
- 
-        # Scan and add DIRECTIVE. 
-        self.tokens.append(self.scan_directive()) 
- 
-    def fetch_document_start(self): 
-        self.fetch_document_indicator(DocumentStartToken) 
- 
-    def fetch_document_end(self): 
-        self.fetch_document_indicator(DocumentEndToken) 
- 
-    def fetch_document_indicator(self, TokenClass): 
- 
+        self.unwind_indent(-1)
+
+        # Reset simple keys.
+        self.remove_possible_simple_key()
+        self.allow_simple_key = False
+
+        # Scan and add DIRECTIVE.
+        self.tokens.append(self.scan_directive())
+
+    def fetch_document_start(self):
+        self.fetch_document_indicator(DocumentStartToken)
+
+    def fetch_document_end(self):
+        self.fetch_document_indicator(DocumentEndToken)
+
+    def fetch_document_indicator(self, TokenClass):
+
         # Set the current indentation to -1.
-        self.unwind_indent(-1) 
- 
-        # Reset simple keys. Note that there could not be a block collection 
-        # after '---'. 
-        self.remove_possible_simple_key() 
-        self.allow_simple_key = False 
- 
-        # Add DOCUMENT-START or DOCUMENT-END. 
-        start_mark = self.get_mark() 
-        self.forward(3) 
-        end_mark = self.get_mark() 
-        self.tokens.append(TokenClass(start_mark, end_mark)) 
- 
-    def fetch_flow_sequence_start(self): 
-        self.fetch_flow_collection_start(FlowSequenceStartToken) 
- 
-    def fetch_flow_mapping_start(self): 
-        self.fetch_flow_collection_start(FlowMappingStartToken) 
- 
-    def fetch_flow_collection_start(self, TokenClass): 
- 
-        # '[' and '{' may start a simple key. 
-        self.save_possible_simple_key() 
- 
-        # Increase the flow level. 
-        self.flow_level += 1 
- 
-        # Simple keys are allowed after '[' and '{'. 
-        self.allow_simple_key = True 
- 
-        # Add FLOW-SEQUENCE-START or FLOW-MAPPING-START. 
-        start_mark = self.get_mark() 
-        self.forward() 
-        end_mark = self.get_mark() 
-        self.tokens.append(TokenClass(start_mark, end_mark)) 
- 
-    def fetch_flow_sequence_end(self): 
-        self.fetch_flow_collection_end(FlowSequenceEndToken) 
- 
-    def fetch_flow_mapping_end(self): 
-        self.fetch_flow_collection_end(FlowMappingEndToken) 
- 
-    def fetch_flow_collection_end(self, TokenClass): 
- 
-        # Reset possible simple key on the current level. 
-        self.remove_possible_simple_key() 
- 
-        # Decrease the flow level. 
-        self.flow_level -= 1 
- 
-        # No simple keys after ']' or '}'. 
-        self.allow_simple_key = False 
- 
-        # Add FLOW-SEQUENCE-END or FLOW-MAPPING-END. 
-        start_mark = self.get_mark() 
-        self.forward() 
-        end_mark = self.get_mark() 
-        self.tokens.append(TokenClass(start_mark, end_mark)) 
- 
-    def fetch_flow_entry(self): 
- 
-        # Simple keys are allowed after ','. 
-        self.allow_simple_key = True 
- 
-        # Reset possible simple key on the current level. 
-        self.remove_possible_simple_key() 
- 
-        # Add FLOW-ENTRY. 
-        start_mark = self.get_mark() 
-        self.forward() 
-        end_mark = self.get_mark() 
-        self.tokens.append(FlowEntryToken(start_mark, end_mark)) 
- 
-    def fetch_block_entry(self): 
- 
-        # Block context needs additional checks. 
-        if not self.flow_level: 
- 
-            # Are we allowed to start a new entry? 
-            if not self.allow_simple_key: 
-                raise ScannerError(None, None, 
-                        "sequence entries are not allowed here", 
-                        self.get_mark()) 
- 
-            # We may need to add BLOCK-SEQUENCE-START. 
-            if self.add_indent(self.column): 
-                mark = self.get_mark() 
-                self.tokens.append(BlockSequenceStartToken(mark, mark)) 
- 
-        # It's an error for the block entry to occur in the flow context, 
-        # but we let the parser detect this. 
-        else: 
-            pass 
- 
-        # Simple keys are allowed after '-'. 
-        self.allow_simple_key = True 
- 
-        # Reset possible simple key on the current level. 
-        self.remove_possible_simple_key() 
- 
-        # Add BLOCK-ENTRY. 
-        start_mark = self.get_mark() 
-        self.forward() 
-        end_mark = self.get_mark() 
-        self.tokens.append(BlockEntryToken(start_mark, end_mark)) 
- 
-    def fetch_key(self): 
-         
-        # Block context needs additional checks. 
-        if not self.flow_level: 
- 
+        self.unwind_indent(-1)
+
+        # Reset simple keys. Note that there could not be a block collection
+        # after '---'.
+        self.remove_possible_simple_key()
+        self.allow_simple_key = False
+
+        # Add DOCUMENT-START or DOCUMENT-END.
+        start_mark = self.get_mark()
+        self.forward(3)
+        end_mark = self.get_mark()
+        self.tokens.append(TokenClass(start_mark, end_mark))
+
+    def fetch_flow_sequence_start(self):
+        self.fetch_flow_collection_start(FlowSequenceStartToken)
+
+    def fetch_flow_mapping_start(self):
+        self.fetch_flow_collection_start(FlowMappingStartToken)
+
+    def fetch_flow_collection_start(self, TokenClass):
+
+        # '[' and '{' may start a simple key.
+        self.save_possible_simple_key()
+
+        # Increase the flow level.
+        self.flow_level += 1
+
+        # Simple keys are allowed after '[' and '{'.
+        self.allow_simple_key = True
+
+        # Add FLOW-SEQUENCE-START or FLOW-MAPPING-START.
+        start_mark = self.get_mark()
+        self.forward()
+        end_mark = self.get_mark()
+        self.tokens.append(TokenClass(start_mark, end_mark))
+
+    def fetch_flow_sequence_end(self):
+        self.fetch_flow_collection_end(FlowSequenceEndToken)
+
+    def fetch_flow_mapping_end(self):
+        self.fetch_flow_collection_end(FlowMappingEndToken)
+
+    def fetch_flow_collection_end(self, TokenClass):
+
+        # Reset possible simple key on the current level.
+        self.remove_possible_simple_key()
+
+        # Decrease the flow level.
+        self.flow_level -= 1
+
+        # No simple keys after ']' or '}'.
+        self.allow_simple_key = False
+
+        # Add FLOW-SEQUENCE-END or FLOW-MAPPING-END.
+        start_mark = self.get_mark()
+        self.forward()
+        end_mark = self.get_mark()
+        self.tokens.append(TokenClass(start_mark, end_mark))
+
+    def fetch_flow_entry(self):
+
+        # Simple keys are allowed after ','.
+        self.allow_simple_key = True
+
+        # Reset possible simple key on the current level.
+        self.remove_possible_simple_key()
+
+        # Add FLOW-ENTRY.
+        start_mark = self.get_mark()
+        self.forward()
+        end_mark = self.get_mark()
+        self.tokens.append(FlowEntryToken(start_mark, end_mark))
+
+    def fetch_block_entry(self):
+
+        # Block context needs additional checks.
+        if not self.flow_level:
+
+            # Are we allowed to start a new entry?
+            if not self.allow_simple_key:
+                raise ScannerError(None, None,
+                        "sequence entries are not allowed here",
+                        self.get_mark())
+
+            # We may need to add BLOCK-SEQUENCE-START.
+            if self.add_indent(self.column):
+                mark = self.get_mark()
+                self.tokens.append(BlockSequenceStartToken(mark, mark))
+
+        # It's an error for the block entry to occur in the flow context,
+        # but we let the parser detect this.
+        else:
+            pass
+
+        # Simple keys are allowed after '-'.
+        self.allow_simple_key = True
+
+        # Reset possible simple key on the current level.
+        self.remove_possible_simple_key()
+
+        # Add BLOCK-ENTRY.
+        start_mark = self.get_mark()
+        self.forward()
+        end_mark = self.get_mark()
+        self.tokens.append(BlockEntryToken(start_mark, end_mark))
+
+    def fetch_key(self):
+        
+        # Block context needs additional checks.
+        if not self.flow_level:
+
             # Are we allowed to start a key (not necessary a simple)?
-            if not self.allow_simple_key: 
-                raise ScannerError(None, None, 
-                        "mapping keys are not allowed here", 
-                        self.get_mark()) 
- 
-            # We may need to add BLOCK-MAPPING-START. 
-            if self.add_indent(self.column): 
-                mark = self.get_mark() 
-                self.tokens.append(BlockMappingStartToken(mark, mark)) 
- 
-        # Simple keys are allowed after '?' in the block context. 
-        self.allow_simple_key = not self.flow_level 
- 
-        # Reset possible simple key on the current level. 
-        self.remove_possible_simple_key() 
- 
-        # Add KEY. 
-        start_mark = self.get_mark() 
-        self.forward() 
-        end_mark = self.get_mark() 
-        self.tokens.append(KeyToken(start_mark, end_mark)) 
- 
-    def fetch_value(self): 
- 
-        # Do we determine a simple key? 
-        if self.flow_level in self.possible_simple_keys: 
- 
-            # Add KEY. 
-            key = self.possible_simple_keys[self.flow_level] 
-            del self.possible_simple_keys[self.flow_level] 
-            self.tokens.insert(key.token_number-self.tokens_taken, 
-                    KeyToken(key.mark, key.mark)) 
- 
-            # If this key starts a new block mapping, we need to add 
-            # BLOCK-MAPPING-START. 
-            if not self.flow_level: 
-                if self.add_indent(key.column): 
-                    self.tokens.insert(key.token_number-self.tokens_taken, 
-                            BlockMappingStartToken(key.mark, key.mark)) 
- 
-            # There cannot be two simple keys one after another. 
-            self.allow_simple_key = False 
- 
-        # It must be a part of a complex key. 
-        else: 
-             
-            # Block context needs additional checks. 
+            if not self.allow_simple_key:
+                raise ScannerError(None, None,
+                        "mapping keys are not allowed here",
+                        self.get_mark())
+
+            # We may need to add BLOCK-MAPPING-START.
+            if self.add_indent(self.column):
+                mark = self.get_mark()
+                self.tokens.append(BlockMappingStartToken(mark, mark))
+
+        # Simple keys are allowed after '?' in the block context.
+        self.allow_simple_key = not self.flow_level
+
+        # Reset possible simple key on the current level.
+        self.remove_possible_simple_key()
+
+        # Add KEY.
+        start_mark = self.get_mark()
+        self.forward()
+        end_mark = self.get_mark()
+        self.tokens.append(KeyToken(start_mark, end_mark))
+
+    def fetch_value(self):
+
+        # Do we determine a simple key?
+        if self.flow_level in self.possible_simple_keys:
+
+            # Add KEY.
+            key = self.possible_simple_keys[self.flow_level]
+            del self.possible_simple_keys[self.flow_level]
+            self.tokens.insert(key.token_number-self.tokens_taken,
+                    KeyToken(key.mark, key.mark))
+
+            # If this key starts a new block mapping, we need to add
+            # BLOCK-MAPPING-START.
+            if not self.flow_level:
+                if self.add_indent(key.column):
+                    self.tokens.insert(key.token_number-self.tokens_taken,
+                            BlockMappingStartToken(key.mark, key.mark))
+
+            # There cannot be two simple keys one after another.
+            self.allow_simple_key = False
+
+        # It must be a part of a complex key.
+        else:
+            
+            # Block context needs additional checks.
             # (Do we really need them? They will be caught by the parser
-            # anyway.) 
-            if not self.flow_level: 
- 
-                # We are allowed to start a complex value if and only if 
-                # we can start a simple key. 
-                if not self.allow_simple_key: 
-                    raise ScannerError(None, None, 
-                            "mapping values are not allowed here", 
-                            self.get_mark()) 
- 
-            # If this value starts a new block mapping, we need to add 
-            # BLOCK-MAPPING-START.  It will be detected as an error later by 
-            # the parser. 
-            if not self.flow_level: 
-                if self.add_indent(self.column): 
-                    mark = self.get_mark() 
-                    self.tokens.append(BlockMappingStartToken(mark, mark)) 
- 
-            # Simple keys are allowed after ':' in the block context. 
-            self.allow_simple_key = not self.flow_level 
- 
-            # Reset possible simple key on the current level. 
-            self.remove_possible_simple_key() 
- 
-        # Add VALUE. 
-        start_mark = self.get_mark() 
-        self.forward() 
-        end_mark = self.get_mark() 
-        self.tokens.append(ValueToken(start_mark, end_mark)) 
- 
-    def fetch_alias(self): 
- 
-        # ALIAS could be a simple key. 
-        self.save_possible_simple_key() 
- 
-        # No simple keys after ALIAS. 
-        self.allow_simple_key = False 
- 
-        # Scan and add ALIAS. 
-        self.tokens.append(self.scan_anchor(AliasToken)) 
- 
-    def fetch_anchor(self): 
- 
-        # ANCHOR could start a simple key. 
-        self.save_possible_simple_key() 
- 
-        # No simple keys after ANCHOR. 
-        self.allow_simple_key = False 
- 
-        # Scan and add ANCHOR. 
-        self.tokens.append(self.scan_anchor(AnchorToken)) 
- 
-    def fetch_tag(self): 
- 
-        # TAG could start a simple key. 
-        self.save_possible_simple_key() 
- 
-        # No simple keys after TAG. 
-        self.allow_simple_key = False 
- 
-        # Scan and add TAG. 
-        self.tokens.append(self.scan_tag()) 
- 
-    def fetch_literal(self): 
-        self.fetch_block_scalar(style='|') 
- 
-    def fetch_folded(self): 
-        self.fetch_block_scalar(style='>') 
- 
-    def fetch_block_scalar(self, style): 
- 
-        # A simple key may follow a block scalar. 
-        self.allow_simple_key = True 
- 
-        # Reset possible simple key on the current level. 
-        self.remove_possible_simple_key() 
- 
-        # Scan and add SCALAR. 
-        self.tokens.append(self.scan_block_scalar(style)) 
- 
-    def fetch_single(self): 
-        self.fetch_flow_scalar(style='\'') 
- 
-    def fetch_double(self): 
-        self.fetch_flow_scalar(style='"') 
- 
-    def fetch_flow_scalar(self, style): 
- 
-        # A flow scalar could be a simple key. 
-        self.save_possible_simple_key() 
- 
-        # No simple keys after flow scalars. 
-        self.allow_simple_key = False 
- 
-        # Scan and add SCALAR. 
-        self.tokens.append(self.scan_flow_scalar(style)) 
- 
-    def fetch_plain(self): 
- 
-        # A plain scalar could be a simple key. 
-        self.save_possible_simple_key() 
- 
-        # No simple keys after plain scalars. But note that `scan_plain` will 
-        # change this flag if the scan is finished at the beginning of the 
-        # line. 
-        self.allow_simple_key = False 
- 
-        # Scan and add SCALAR. May change `allow_simple_key`. 
-        self.tokens.append(self.scan_plain()) 
- 
-    # Checkers. 
- 
-    def check_directive(self): 
- 
-        # DIRECTIVE:        ^ '%' ... 
-        # The '%' indicator is already checked. 
-        if self.column == 0: 
-            return True 
- 
-    def check_document_start(self): 
- 
-        # DOCUMENT-START:   ^ '---' (' '|'\n') 
-        if self.column == 0: 
-            if self.prefix(3) == '---'  \ 
-                    and self.peek(3) in '\0 \t\r\n\x85\u2028\u2029': 
-                return True 
- 
-    def check_document_end(self): 
- 
-        # DOCUMENT-END:     ^ '...' (' '|'\n') 
-        if self.column == 0: 
-            if self.prefix(3) == '...'  \ 
-                    and self.peek(3) in '\0 \t\r\n\x85\u2028\u2029': 
-                return True 
- 
-    def check_block_entry(self): 
- 
-        # BLOCK-ENTRY:      '-' (' '|'\n') 
-        return self.peek(1) in '\0 \t\r\n\x85\u2028\u2029' 
- 
-    def check_key(self): 
- 
-        # KEY(flow context):    '?' 
-        if self.flow_level: 
-            return True 
- 
-        # KEY(block context):   '?' (' '|'\n') 
-        else: 
-            return self.peek(1) in '\0 \t\r\n\x85\u2028\u2029' 
- 
-    def check_value(self): 
- 
-        # VALUE(flow context):  ':' 
-        if self.flow_level: 
-            return True 
- 
-        # VALUE(block context): ':' (' '|'\n') 
-        else: 
-            return self.peek(1) in '\0 \t\r\n\x85\u2028\u2029' 
- 
-    def check_plain(self): 
- 
-        # A plain scalar may start with any non-space character except: 
-        #   '-', '?', ':', ',', '[', ']', '{', '}', 
-        #   '#', '&', '*', '!', '|', '>', '\'', '\"', 
-        #   '%', '@', '`'. 
-        # 
-        # It may also start with 
-        #   '-', '?', ':' 
-        # if it is followed by a non-space character. 
-        # 
-        # Note that we limit the last rule to the block context (except the 
-        # '-' character) because we want the flow context to be space 
-        # independent. 
-        ch = self.peek() 
-        return ch not in '\0 \t\r\n\x85\u2028\u2029-?:,[]{}#&*!|>\'\"%@`'  \ 
-                or (self.peek(1) not in '\0 \t\r\n\x85\u2028\u2029' 
-                        and (ch == '-' or (not self.flow_level and ch in '?:'))) 
- 
-    # Scanners. 
- 
-    def scan_to_next_token(self): 
-        # We ignore spaces, line breaks and comments. 
-        # If we find a line break in the block context, we set the flag 
-        # `allow_simple_key` on. 
-        # The byte order mark is stripped if it's the first character in the 
-        # stream. We do not yet support BOM inside the stream as the 
-        # specification requires. Any such mark will be considered as a part 
-        # of the document. 
-        # 
-        # TODO: We need to make tab handling rules more sane. A good rule is 
-        #   Tabs cannot precede tokens 
-        #   BLOCK-SEQUENCE-START, BLOCK-MAPPING-START, BLOCK-END, 
-        #   KEY(block), VALUE(block), BLOCK-ENTRY 
-        # So the checking code is 
-        #   if <TAB>: 
-        #       self.allow_simple_keys = False 
-        # We also need to add the check for `allow_simple_keys == True` to 
-        # `unwind_indent` before issuing BLOCK-END. 
-        # Scanners for block, flow, and plain scalars need to be modified. 
- 
-        if self.index == 0 and self.peek() == '\uFEFF': 
-            self.forward() 
-        found = False 
-        while not found: 
-            while self.peek() == ' ': 
-                self.forward() 
-            if self.peek() == '#': 
-                while self.peek() not in '\0\r\n\x85\u2028\u2029': 
-                    self.forward() 
-            if self.scan_line_break(): 
-                if not self.flow_level: 
-                    self.allow_simple_key = True 
-            else: 
-                found = True 
- 
-    def scan_directive(self): 
-        # See the specification for details. 
-        start_mark = self.get_mark() 
-        self.forward() 
-        name = self.scan_directive_name(start_mark) 
-        value = None 
-        if name == 'YAML': 
-            value = self.scan_yaml_directive_value(start_mark) 
-            end_mark = self.get_mark() 
-        elif name == 'TAG': 
-            value = self.scan_tag_directive_value(start_mark) 
-            end_mark = self.get_mark() 
-        else: 
-            end_mark = self.get_mark() 
-            while self.peek() not in '\0\r\n\x85\u2028\u2029': 
-                self.forward() 
-        self.scan_directive_ignored_line(start_mark) 
-        return DirectiveToken(name, value, start_mark, end_mark) 
- 
-    def scan_directive_name(self, start_mark): 
-        # See the specification for details. 
-        length = 0 
-        ch = self.peek(length) 
-        while '0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z'  \ 
-                or ch in '-_': 
-            length += 1 
-            ch = self.peek(length) 
-        if not length: 
-            raise ScannerError("while scanning a directive", start_mark, 
-                    "expected alphabetic or numeric character, but found %r" 
-                    % ch, self.get_mark()) 
-        value = self.prefix(length) 
-        self.forward(length) 
-        ch = self.peek() 
-        if ch not in '\0 \r\n\x85\u2028\u2029': 
-            raise ScannerError("while scanning a directive", start_mark, 
-                    "expected alphabetic or numeric character, but found %r" 
-                    % ch, self.get_mark()) 
-        return value 
- 
-    def scan_yaml_directive_value(self, start_mark): 
-        # See the specification for details. 
-        while self.peek() == ' ': 
-            self.forward() 
-        major = self.scan_yaml_directive_number(start_mark) 
-        if self.peek() != '.': 
-            raise ScannerError("while scanning a directive", start_mark, 
-                    "expected a digit or '.', but found %r" % self.peek(), 
-                    self.get_mark()) 
-        self.forward() 
-        minor = self.scan_yaml_directive_number(start_mark) 
-        if self.peek() not in '\0 \r\n\x85\u2028\u2029': 
-            raise ScannerError("while scanning a directive", start_mark, 
-                    "expected a digit or ' ', but found %r" % self.peek(), 
-                    self.get_mark()) 
-        return (major, minor) 
- 
-    def scan_yaml_directive_number(self, start_mark): 
-        # See the specification for details. 
-        ch = self.peek() 
-        if not ('0' <= ch <= '9'): 
-            raise ScannerError("while scanning a directive", start_mark, 
-                    "expected a digit, but found %r" % ch, self.get_mark()) 
-        length = 0 
-        while '0' <= self.peek(length) <= '9': 
-            length += 1 
-        value = int(self.prefix(length)) 
-        self.forward(length) 
-        return value 
- 
-    def scan_tag_directive_value(self, start_mark): 
-        # See the specification for details. 
-        while self.peek() == ' ': 
-            self.forward() 
-        handle = self.scan_tag_directive_handle(start_mark) 
-        while self.peek() == ' ': 
-            self.forward() 
-        prefix = self.scan_tag_directive_prefix(start_mark) 
-        return (handle, prefix) 
- 
-    def scan_tag_directive_handle(self, start_mark): 
-        # See the specification for details. 
-        value = self.scan_tag_handle('directive', start_mark) 
-        ch = self.peek() 
-        if ch != ' ': 
-            raise ScannerError("while scanning a directive", start_mark, 
-                    "expected ' ', but found %r" % ch, self.get_mark()) 
-        return value 
- 
-    def scan_tag_directive_prefix(self, start_mark): 
-        # See the specification for details. 
-        value = self.scan_tag_uri('directive', start_mark) 
-        ch = self.peek() 
-        if ch not in '\0 \r\n\x85\u2028\u2029': 
-            raise ScannerError("while scanning a directive", start_mark, 
-                    "expected ' ', but found %r" % ch, self.get_mark()) 
-        return value 
- 
-    def scan_directive_ignored_line(self, start_mark): 
-        # See the specification for details. 
-        while self.peek() == ' ': 
-            self.forward() 
-        if self.peek() == '#': 
-            while self.peek() not in '\0\r\n\x85\u2028\u2029': 
-                self.forward() 
-        ch = self.peek() 
-        if ch not in '\0\r\n\x85\u2028\u2029': 
-            raise ScannerError("while scanning a directive", start_mark, 
-                    "expected a comment or a line break, but found %r" 
-                        % ch, self.get_mark()) 
-        self.scan_line_break() 
- 
-    def scan_anchor(self, TokenClass): 
-        # The specification does not restrict characters for anchors and 
-        # aliases. This may lead to problems, for instance, the document: 
-        #   [ *alias, value ] 
+            # anyway.)
+            if not self.flow_level:
+
+                # We are allowed to start a complex value if and only if
+                # we can start a simple key.
+                if not self.allow_simple_key:
+                    raise ScannerError(None, None,
+                            "mapping values are not allowed here",
+                            self.get_mark())
+
+            # If this value starts a new block mapping, we need to add
+            # BLOCK-MAPPING-START.  It will be detected as an error later by
+            # the parser.
+            if not self.flow_level:
+                if self.add_indent(self.column):
+                    mark = self.get_mark()
+                    self.tokens.append(BlockMappingStartToken(mark, mark))
+
+            # Simple keys are allowed after ':' in the block context.
+            self.allow_simple_key = not self.flow_level
+
+            # Reset possible simple key on the current level.
+            self.remove_possible_simple_key()
+
+        # Add VALUE.
+        start_mark = self.get_mark()
+        self.forward()
+        end_mark = self.get_mark()
+        self.tokens.append(ValueToken(start_mark, end_mark))
+
+    def fetch_alias(self):
+
+        # ALIAS could be a simple key.
+        self.save_possible_simple_key()
+
+        # No simple keys after ALIAS.
+        self.allow_simple_key = False
+
+        # Scan and add ALIAS.
+        self.tokens.append(self.scan_anchor(AliasToken))
+
+    def fetch_anchor(self):
+
+        # ANCHOR could start a simple key.
+        self.save_possible_simple_key()
+
+        # No simple keys after ANCHOR.
+        self.allow_simple_key = False
+
+        # Scan and add ANCHOR.
+        self.tokens.append(self.scan_anchor(AnchorToken))
+
+    def fetch_tag(self):
+
+        # TAG could start a simple key.
+        self.save_possible_simple_key()
+
+        # No simple keys after TAG.
+        self.allow_simple_key = False
+
+        # Scan and add TAG.
+        self.tokens.append(self.scan_tag())
+
+    def fetch_literal(self):
+        self.fetch_block_scalar(style='|')
+
+    def fetch_folded(self):
+        self.fetch_block_scalar(style='>')
+
+    def fetch_block_scalar(self, style):
+
+        # A simple key may follow a block scalar.
+        self.allow_simple_key = True
+
+        # Reset possible simple key on the current level.
+        self.remove_possible_simple_key()
+
+        # Scan and add SCALAR.
+        self.tokens.append(self.scan_block_scalar(style))
+
+    def fetch_single(self):
+        self.fetch_flow_scalar(style='\'')
+
+    def fetch_double(self):
+        self.fetch_flow_scalar(style='"')
+
+    def fetch_flow_scalar(self, style):
+
+        # A flow scalar could be a simple key.
+        self.save_possible_simple_key()
+
+        # No simple keys after flow scalars.
+        self.allow_simple_key = False
+
+        # Scan and add SCALAR.
+        self.tokens.append(self.scan_flow_scalar(style))
+
+    def fetch_plain(self):
+
+        # A plain scalar could be a simple key.
+        self.save_possible_simple_key()
+
+        # No simple keys after plain scalars. But note that `scan_plain` will
+        # change this flag if the scan is finished at the beginning of the
+        # line.
+        self.allow_simple_key = False
+
+        # Scan and add SCALAR. May change `allow_simple_key`.
+        self.tokens.append(self.scan_plain())
+
+    # Checkers.
+
+    def check_directive(self):
+
+        # DIRECTIVE:        ^ '%' ...
+        # The '%' indicator is already checked.
+        if self.column == 0:
+            return True
+
+    def check_document_start(self):
+
+        # DOCUMENT-START:   ^ '---' (' '|'\n')
+        if self.column == 0:
+            if self.prefix(3) == '---'  \
+                    and self.peek(3) in '\0 \t\r\n\x85\u2028\u2029':
+                return True
+
+    def check_document_end(self):
+
+        # DOCUMENT-END:     ^ '...' (' '|'\n')
+        if self.column == 0:
+            if self.prefix(3) == '...'  \
+                    and self.peek(3) in '\0 \t\r\n\x85\u2028\u2029':
+                return True
+
+    def check_block_entry(self):
+
+        # BLOCK-ENTRY:      '-' (' '|'\n')
+        return self.peek(1) in '\0 \t\r\n\x85\u2028\u2029'
+
+    def check_key(self):
+
+        # KEY(flow context):    '?'
+        if self.flow_level:
+            return True
+
+        # KEY(block context):   '?' (' '|'\n')
+        else:
+            return self.peek(1) in '\0 \t\r\n\x85\u2028\u2029'
+
+    def check_value(self):
+
+        # VALUE(flow context):  ':'
+        if self.flow_level:
+            return True
+
+        # VALUE(block context): ':' (' '|'\n')
+        else:
+            return self.peek(1) in '\0 \t\r\n\x85\u2028\u2029'
+
+    def check_plain(self):
+
+        # A plain scalar may start with any non-space character except:
+        #   '-', '?', ':', ',', '[', ']', '{', '}',
+        #   '#', '&', '*', '!', '|', '>', '\'', '\"',
+        #   '%', '@', '`'.
+        #
+        # It may also start with
+        #   '-', '?', ':'
+        # if it is followed by a non-space character.
+        #
+        # Note that we limit the last rule to the block context (except the
+        # '-' character) because we want the flow context to be space
+        # independent.
+        ch = self.peek()
+        return ch not in '\0 \t\r\n\x85\u2028\u2029-?:,[]{}#&*!|>\'\"%@`'  \
+                or (self.peek(1) not in '\0 \t\r\n\x85\u2028\u2029'
+                        and (ch == '-' or (not self.flow_level and ch in '?:')))
+
+    # Scanners.
+
+    def scan_to_next_token(self):
+        # We ignore spaces, line breaks and comments.
+        # If we find a line break in the block context, we set the flag
+        # `allow_simple_key` on.
+        # The byte order mark is stripped if it's the first character in the
+        # stream. We do not yet support BOM inside the stream as the
+        # specification requires. Any such mark will be considered as a part
+        # of the document.
+        #
+        # TODO: We need to make tab handling rules more sane. A good rule is
+        #   Tabs cannot precede tokens
+        #   BLOCK-SEQUENCE-START, BLOCK-MAPPING-START, BLOCK-END,
+        #   KEY(block), VALUE(block), BLOCK-ENTRY
+        # So the checking code is
+        #   if <TAB>:
+        #       self.allow_simple_keys = False
+        # We also need to add the check for `allow_simple_keys == True` to
+        # `unwind_indent` before issuing BLOCK-END.
+        # Scanners for block, flow, and plain scalars need to be modified.
+
+        if self.index == 0 and self.peek() == '\uFEFF':
+            self.forward()
+        found = False
+        while not found:
+            while self.peek() == ' ':
+                self.forward()
+            if self.peek() == '#':
+                while self.peek() not in '\0\r\n\x85\u2028\u2029':
+                    self.forward()
+            if self.scan_line_break():
+                if not self.flow_level:
+                    self.allow_simple_key = True
+            else:
+                found = True
+
+    def scan_directive(self):
+        # See the specification for details.
+        start_mark = self.get_mark()
+        self.forward()
+        name = self.scan_directive_name(start_mark)
+        value = None
+        if name == 'YAML':
+            value = self.scan_yaml_directive_value(start_mark)
+            end_mark = self.get_mark()
+        elif name == 'TAG':
+            value = self.scan_tag_directive_value(start_mark)
+            end_mark = self.get_mark()
+        else:
+            end_mark = self.get_mark()
+            while self.peek() not in '\0\r\n\x85\u2028\u2029':
+                self.forward()
+        self.scan_directive_ignored_line(start_mark)
+        return DirectiveToken(name, value, start_mark, end_mark)
+
+    def scan_directive_name(self, start_mark):
+        # See the specification for details.
+        length = 0
+        ch = self.peek(length)
+        while '0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z'  \
+                or ch in '-_':
+            length += 1
+            ch = self.peek(length)
+        if not length:
+            raise ScannerError("while scanning a directive", start_mark,
+                    "expected alphabetic or numeric character, but found %r"
+                    % ch, self.get_mark())
+        value = self.prefix(length)
+        self.forward(length)
+        ch = self.peek()
+        if ch not in '\0 \r\n\x85\u2028\u2029':
+            raise ScannerError("while scanning a directive", start_mark,
+                    "expected alphabetic or numeric character, but found %r"
+                    % ch, self.get_mark())
+        return value
+
+    def scan_yaml_directive_value(self, start_mark):
+        # See the specification for details.
+        while self.peek() == ' ':
+            self.forward()
+        major = self.scan_yaml_directive_number(start_mark)
+        if self.peek() != '.':
+            raise ScannerError("while scanning a directive", start_mark,
+                    "expected a digit or '.', but found %r" % self.peek(),
+                    self.get_mark())
+        self.forward()
+        minor = self.scan_yaml_directive_number(start_mark)
+        if self.peek() not in '\0 \r\n\x85\u2028\u2029':
+            raise ScannerError("while scanning a directive", start_mark,
+                    "expected a digit or ' ', but found %r" % self.peek(),
+                    self.get_mark())
+        return (major, minor)
+
+    def scan_yaml_directive_number(self, start_mark):
+        # See the specification for details.
+        ch = self.peek()
+        if not ('0' <= ch <= '9'):
+            raise ScannerError("while scanning a directive", start_mark,
+                    "expected a digit, but found %r" % ch, self.get_mark())
+        length = 0
+        while '0' <= self.peek(length) <= '9':
+            length += 1
+        value = int(self.prefix(length))
+        self.forward(length)
+        return value
+
+    def scan_tag_directive_value(self, start_mark):
+        # See the specification for details.
+        while self.peek() == ' ':
+            self.forward()
+        handle = self.scan_tag_directive_handle(start_mark)
+        while self.peek() == ' ':
+            self.forward()
+        prefix = self.scan_tag_directive_prefix(start_mark)
+        return (handle, prefix)
+
+    def scan_tag_directive_handle(self, start_mark):
+        # See the specification for details.
+        value = self.scan_tag_handle('directive', start_mark)
+        ch = self.peek()
+        if ch != ' ':
+            raise ScannerError("while scanning a directive", start_mark,
+                    "expected ' ', but found %r" % ch, self.get_mark())
+        return value
+
+    def scan_tag_directive_prefix(self, start_mark):
+        # See the specification for details.
+        value = self.scan_tag_uri('directive', start_mark)
+        ch = self.peek()
+        if ch not in '\0 \r\n\x85\u2028\u2029':
+            raise ScannerError("while scanning a directive", start_mark,
+                    "expected ' ', but found %r" % ch, self.get_mark())
+        return value
+
+    def scan_directive_ignored_line(self, start_mark):
+        # See the specification for details.
+        while self.peek() == ' ':
+            self.forward()
+        if self.peek() == '#':
+            while self.peek() not in '\0\r\n\x85\u2028\u2029':
+                self.forward()
+        ch = self.peek()
+        if ch not in '\0\r\n\x85\u2028\u2029':
+            raise ScannerError("while scanning a directive", start_mark,
+                    "expected a comment or a line break, but found %r"
+                        % ch, self.get_mark())
+        self.scan_line_break()
+
+    def scan_anchor(self, TokenClass):
+        # The specification does not restrict characters for anchors and
+        # aliases. This may lead to problems, for instance, the document:
+        #   [ *alias, value ]
         # can be interpreted in two ways, as
-        #   [ "value" ] 
-        # and 
-        #   [ *alias , "value" ] 
-        # Therefore we restrict aliases to numbers and ASCII letters. 
-        start_mark = self.get_mark() 
-        indicator = self.peek() 
-        if indicator == '*': 
-            name = 'alias' 
-        else: 
-            name = 'anchor' 
-        self.forward() 
-        length = 0 
-        ch = self.peek(length) 
-        while '0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z'  \ 
-                or ch in '-_': 
-            length += 1 
-            ch = self.peek(length) 
-        if not length: 
-            raise ScannerError("while scanning an %s" % name, start_mark, 
-                    "expected alphabetic or numeric character, but found %r" 
-                    % ch, self.get_mark()) 
-        value = self.prefix(length) 
-        self.forward(length) 
-        ch = self.peek() 
-        if ch not in '\0 \t\r\n\x85\u2028\u2029?:,]}%@`': 
-            raise ScannerError("while scanning an %s" % name, start_mark, 
-                    "expected alphabetic or numeric character, but found %r" 
-                    % ch, self.get_mark()) 
-        end_mark = self.get_mark() 
-        return TokenClass(value, start_mark, end_mark) 
- 
-    def scan_tag(self): 
-        # See the specification for details. 
-        start_mark = self.get_mark() 
-        ch = self.peek(1) 
-        if ch == '<': 
-            handle = None 
-            self.forward(2) 
-            suffix = self.scan_tag_uri('tag', start_mark) 
-            if self.peek() != '>': 
-                raise ScannerError("while parsing a tag", start_mark, 
-                        "expected '>', but found %r" % self.peek(), 
-                        self.get_mark()) 
-            self.forward() 
-        elif ch in '\0 \t\r\n\x85\u2028\u2029': 
-            handle = None 
-            suffix = '!' 
-            self.forward() 
-        else: 
-            length = 1 
-            use_handle = False 
-            while ch not in '\0 \r\n\x85\u2028\u2029': 
-                if ch == '!': 
-                    use_handle = True 
-                    break 
-                length += 1 
-                ch = self.peek(length) 
-            handle = '!' 
-            if use_handle: 
-                handle = self.scan_tag_handle('tag', start_mark) 
-            else: 
-                handle = '!' 
-                self.forward() 
-            suffix = self.scan_tag_uri('tag', start_mark) 
-        ch = self.peek() 
-        if ch not in '\0 \r\n\x85\u2028\u2029': 
-            raise ScannerError("while scanning a tag", start_mark, 
-                    "expected ' ', but found %r" % ch, self.get_mark()) 
-        value = (handle, suffix) 
-        end_mark = self.get_mark() 
-        return TagToken(value, start_mark, end_mark) 
- 
-    def scan_block_scalar(self, style): 
-        # See the specification for details. 
- 
-        if style == '>': 
-            folded = True 
-        else: 
-            folded = False 
- 
-        chunks = [] 
-        start_mark = self.get_mark() 
- 
-        # Scan the header. 
-        self.forward() 
-        chomping, increment = self.scan_block_scalar_indicators(start_mark) 
-        self.scan_block_scalar_ignored_line(start_mark) 
- 
-        # Determine the indentation level and go to the first non-empty line. 
-        min_indent = self.indent+1 
-        if min_indent < 1: 
-            min_indent = 1 
-        if increment is None: 
-            breaks, max_indent, end_mark = self.scan_block_scalar_indentation() 
-            indent = max(min_indent, max_indent) 
-        else: 
-            indent = min_indent+increment-1 
-            breaks, end_mark = self.scan_block_scalar_breaks(indent) 
-        line_break = '' 
- 
-        # Scan the inner part of the block scalar. 
-        while self.column == indent and self.peek() != '\0': 
-            chunks.extend(breaks) 
-            leading_non_space = self.peek() not in ' \t' 
-            length = 0 
-            while self.peek(length) not in '\0\r\n\x85\u2028\u2029': 
-                length += 1 
-            chunks.append(self.prefix(length)) 
-            self.forward(length) 
-            line_break = self.scan_line_break() 
-            breaks, end_mark = self.scan_block_scalar_breaks(indent) 
-            if self.column == indent and self.peek() != '\0': 
- 
-                # Unfortunately, folding rules are ambiguous. 
-                # 
-                # This is the folding according to the specification: 
-                 
-                if folded and line_break == '\n'    \ 
-                        and leading_non_space and self.peek() not in ' \t': 
-                    if not breaks: 
-                        chunks.append(' ') 
-                else: 
-                    chunks.append(line_break) 
-                 
-                # This is Clark Evans's interpretation (also in the spec 
-                # examples): 
-                # 
-                #if folded and line_break == '\n': 
-                #    if not breaks: 
-                #        if self.peek() not in ' \t': 
-                #            chunks.append(' ') 
-                #        else: 
-                #            chunks.append(line_break) 
-                #else: 
-                #    chunks.append(line_break) 
-            else: 
-                break 
- 
-        # Chomp the tail. 
-        if chomping is not False: 
-            chunks.append(line_break) 
-        if chomping is True: 
-            chunks.extend(breaks) 
- 
-        # We are done. 
-        return ScalarToken(''.join(chunks), False, start_mark, end_mark, 
-                style) 
- 
-    def scan_block_scalar_indicators(self, start_mark): 
-        # See the specification for details. 
-        chomping = None 
-        increment = None 
-        ch = self.peek() 
-        if ch in '+-': 
-            if ch == '+': 
-                chomping = True 
-            else: 
-                chomping = False 
-            self.forward() 
-            ch = self.peek() 
-            if ch in '0123456789': 
-                increment = int(ch) 
-                if increment == 0: 
-                    raise ScannerError("while scanning a block scalar", start_mark, 
-                            "expected indentation indicator in the range 1-9, but found 0", 
-                            self.get_mark()) 
-                self.forward() 
-        elif ch in '0123456789': 
-            increment = int(ch) 
-            if increment == 0: 
-                raise ScannerError("while scanning a block scalar", start_mark, 
-                        "expected indentation indicator in the range 1-9, but found 0", 
-                        self.get_mark()) 
-            self.forward() 
-            ch = self.peek() 
-            if ch in '+-': 
-                if ch == '+': 
-                    chomping = True 
-                else: 
-                    chomping = False 
-                self.forward() 
-        ch = self.peek() 
-        if ch not in '\0 \r\n\x85\u2028\u2029': 
-            raise ScannerError("while scanning a block scalar", start_mark, 
-                    "expected chomping or indentation indicators, but found %r" 
-                    % ch, self.get_mark()) 
-        return chomping, increment 
- 
-    def scan_block_scalar_ignored_line(self, start_mark): 
-        # See the specification for details. 
-        while self.peek() == ' ': 
-            self.forward() 
-        if self.peek() == '#': 
-            while self.peek() not in '\0\r\n\x85\u2028\u2029': 
-                self.forward() 
-        ch = self.peek() 
-        if ch not in '\0\r\n\x85\u2028\u2029': 
-            raise ScannerError("while scanning a block scalar", start_mark, 
-                    "expected a comment or a line break, but found %r" % ch, 
-                    self.get_mark()) 
-        self.scan_line_break() 
- 
-    def scan_block_scalar_indentation(self): 
-        # See the specification for details. 
-        chunks = [] 
-        max_indent = 0 
-        end_mark = self.get_mark() 
-        while self.peek() in ' \r\n\x85\u2028\u2029': 
-            if self.peek() != ' ': 
-                chunks.append(self.scan_line_break()) 
-                end_mark = self.get_mark() 
-            else: 
-                self.forward() 
-                if self.column > max_indent: 
-                    max_indent = self.column 
-        return chunks, max_indent, end_mark 
- 
-    def scan_block_scalar_breaks(self, indent): 
-        # See the specification for details. 
-        chunks = [] 
-        end_mark = self.get_mark() 
-        while self.column < indent and self.peek() == ' ': 
-            self.forward() 
-        while self.peek() in '\r\n\x85\u2028\u2029': 
-            chunks.append(self.scan_line_break()) 
-            end_mark = self.get_mark() 
-            while self.column < indent and self.peek() == ' ': 
-                self.forward() 
-        return chunks, end_mark 
- 
-    def scan_flow_scalar(self, style): 
-        # See the specification for details. 
-        # Note that we loose indentation rules for quoted scalars. Quoted 
-        # scalars don't need to adhere indentation because " and ' clearly 
-        # mark the beginning and the end of them. Therefore we are less 
-        # restrictive then the specification requires. We only need to check 
-        # that document separators are not included in scalars. 
-        if style == '"': 
-            double = True 
-        else: 
-            double = False 
-        chunks = [] 
-        start_mark = self.get_mark() 
-        quote = self.peek() 
-        self.forward() 
-        chunks.extend(self.scan_flow_scalar_non_spaces(double, start_mark)) 
-        while self.peek() != quote: 
-            chunks.extend(self.scan_flow_scalar_spaces(double, start_mark)) 
-            chunks.extend(self.scan_flow_scalar_non_spaces(double, start_mark)) 
-        self.forward() 
-        end_mark = self.get_mark() 
-        return ScalarToken(''.join(chunks), False, start_mark, end_mark, 
-                style) 
- 
-    ESCAPE_REPLACEMENTS = { 
-        '0':    '\0', 
-        'a':    '\x07', 
-        'b':    '\x08', 
-        't':    '\x09', 
-        '\t':   '\x09', 
-        'n':    '\x0A', 
-        'v':    '\x0B', 
-        'f':    '\x0C', 
-        'r':    '\x0D', 
-        'e':    '\x1B', 
-        ' ':    '\x20', 
-        '\"':   '\"', 
-        '\\':   '\\', 
+        #   [ "value" ]
+        # and
+        #   [ *alias , "value" ]
+        # Therefore we restrict aliases to numbers and ASCII letters.
+        start_mark = self.get_mark()
+        indicator = self.peek()
+        if indicator == '*':
+            name = 'alias'
+        else:
+            name = 'anchor'
+        self.forward()
+        length = 0
+        ch = self.peek(length)
+        while '0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z'  \
+                or ch in '-_':
+            length += 1
+            ch = self.peek(length)
+        if not length:
+            raise ScannerError("while scanning an %s" % name, start_mark,
+                    "expected alphabetic or numeric character, but found %r"
+                    % ch, self.get_mark())
+        value = self.prefix(length)
+        self.forward(length)
+        ch = self.peek()
+        if ch not in '\0 \t\r\n\x85\u2028\u2029?:,]}%@`':
+            raise ScannerError("while scanning an %s" % name, start_mark,
+                    "expected alphabetic or numeric character, but found %r"
+                    % ch, self.get_mark())
+        end_mark = self.get_mark()
+        return TokenClass(value, start_mark, end_mark)
+
+    def scan_tag(self):
+        # See the specification for details.
+        start_mark = self.get_mark()
+        ch = self.peek(1)
+        if ch == '<':
+            handle = None
+            self.forward(2)
+            suffix = self.scan_tag_uri('tag', start_mark)
+            if self.peek() != '>':
+                raise ScannerError("while parsing a tag", start_mark,
+                        "expected '>', but found %r" % self.peek(),
+                        self.get_mark())
+            self.forward()
+        elif ch in '\0 \t\r\n\x85\u2028\u2029':
+            handle = None
+            suffix = '!'
+            self.forward()
+        else:
+            length = 1
+            use_handle = False
+            while ch not in '\0 \r\n\x85\u2028\u2029':
+                if ch == '!':
+                    use_handle = True
+                    break
+                length += 1
+                ch = self.peek(length)
+            handle = '!'
+            if use_handle:
+                handle = self.scan_tag_handle('tag', start_mark)
+            else:
+                handle = '!'
+                self.forward()
+            suffix = self.scan_tag_uri('tag', start_mark)
+        ch = self.peek()
+        if ch not in '\0 \r\n\x85\u2028\u2029':
+            raise ScannerError("while scanning a tag", start_mark,
+                    "expected ' ', but found %r" % ch, self.get_mark())
+        value = (handle, suffix)
+        end_mark = self.get_mark()
+        return TagToken(value, start_mark, end_mark)
+
+    def scan_block_scalar(self, style):
+        # See the specification for details.
+
+        if style == '>':
+            folded = True
+        else:
+            folded = False
+
+        chunks = []
+        start_mark = self.get_mark()
+
+        # Scan the header.
+        self.forward()
+        chomping, increment = self.scan_block_scalar_indicators(start_mark)
+        self.scan_block_scalar_ignored_line(start_mark)
+
+        # Determine the indentation level and go to the first non-empty line.
+        min_indent = self.indent+1
+        if min_indent < 1:
+            min_indent = 1
+        if increment is None:
+            breaks, max_indent, end_mark = self.scan_block_scalar_indentation()
+            indent = max(min_indent, max_indent)
+        else:
+            indent = min_indent+increment-1
+            breaks, end_mark = self.scan_block_scalar_breaks(indent)
+        line_break = ''
+
+        # Scan the inner part of the block scalar.
+        while self.column == indent and self.peek() != '\0':
+            chunks.extend(breaks)
+            leading_non_space = self.peek() not in ' \t'
+            length = 0
+            while self.peek(length) not in '\0\r\n\x85\u2028\u2029':
+                length += 1
+            chunks.append(self.prefix(length))
+            self.forward(length)
+            line_break = self.scan_line_break()
+            breaks, end_mark = self.scan_block_scalar_breaks(indent)
+            if self.column == indent and self.peek() != '\0':
+
+                # Unfortunately, folding rules are ambiguous.
+                #
+                # This is the folding according to the specification:
+                
+                if folded and line_break == '\n'    \
+                        and leading_non_space and self.peek() not in ' \t':
+                    if not breaks:
+                        chunks.append(' ')
+                else:
+                    chunks.append(line_break)
+                
+                # This is Clark Evans's interpretation (also in the spec
+                # examples):
+                #
+                #if folded and line_break == '\n':
+                #    if not breaks:
+                #        if self.peek() not in ' \t':
+                #            chunks.append(' ')
+                #        else:
+                #            chunks.append(line_break)
+                #else:
+                #    chunks.append(line_break)
+            else:
+                break
+
+        # Chomp the tail.
+        if chomping is not False:
+            chunks.append(line_break)
+        if chomping is True:
+            chunks.extend(breaks)
+
+        # We are done.
+        return ScalarToken(''.join(chunks), False, start_mark, end_mark,
+                style)
+
+    def scan_block_scalar_indicators(self, start_mark):
+        # See the specification for details.
+        chomping = None
+        increment = None
+        ch = self.peek()
+        if ch in '+-':
+            if ch == '+':
+                chomping = True
+            else:
+                chomping = False
+            self.forward()
+            ch = self.peek()
+            if ch in '0123456789':
+                increment = int(ch)
+                if increment == 0:
+                    raise ScannerError("while scanning a block scalar", start_mark,
+                            "expected indentation indicator in the range 1-9, but found 0",
+                            self.get_mark())
+                self.forward()
+        elif ch in '0123456789':
+            increment = int(ch)
+            if increment == 0:
+                raise ScannerError("while scanning a block scalar", start_mark,
+                        "expected indentation indicator in the range 1-9, but found 0",
+                        self.get_mark())
+            self.forward()
+            ch = self.peek()
+            if ch in '+-':
+                if ch == '+':
+                    chomping = True
+                else:
+                    chomping = False
+                self.forward()
+        ch = self.peek()
+        if ch not in '\0 \r\n\x85\u2028\u2029':
+            raise ScannerError("while scanning a block scalar", start_mark,
+                    "expected chomping or indentation indicators, but found %r"
+                    % ch, self.get_mark())
+        return chomping, increment
+
+    def scan_block_scalar_ignored_line(self, start_mark):
+        # See the specification for details.
+        while self.peek() == ' ':
+            self.forward()
+        if self.peek() == '#':
+            while self.peek() not in '\0\r\n\x85\u2028\u2029':
+                self.forward()
+        ch = self.peek()
+        if ch not in '\0\r\n\x85\u2028\u2029':
+            raise ScannerError("while scanning a block scalar", start_mark,
+                    "expected a comment or a line break, but found %r" % ch,
+                    self.get_mark())
+        self.scan_line_break()
+
+    def scan_block_scalar_indentation(self):
+        # See the specification for details.
+        chunks = []
+        max_indent = 0
+        end_mark = self.get_mark()
+        while self.peek() in ' \r\n\x85\u2028\u2029':
+            if self.peek() != ' ':
+                chunks.append(self.scan_line_break())
+                end_mark = self.get_mark()
+            else:
+                self.forward()
+                if self.column > max_indent:
+                    max_indent = self.column
+        return chunks, max_indent, end_mark
+
+    def scan_block_scalar_breaks(self, indent):
+        # See the specification for details.
+        chunks = []
+        end_mark = self.get_mark()
+        while self.column < indent and self.peek() == ' ':
+            self.forward()
+        while self.peek() in '\r\n\x85\u2028\u2029':
+            chunks.append(self.scan_line_break())
+            end_mark = self.get_mark()
+            while self.column < indent and self.peek() == ' ':
+                self.forward()
+        return chunks, end_mark
+
+    def scan_flow_scalar(self, style):
+        # See the specification for details.
+        # Note that we loose indentation rules for quoted scalars. Quoted
+        # scalars don't need to adhere indentation because " and ' clearly
+        # mark the beginning and the end of them. Therefore we are less
+        # restrictive then the specification requires. We only need to check
+        # that document separators are not included in scalars.
+        if style == '"':
+            double = True
+        else:
+            double = False
+        chunks = []
+        start_mark = self.get_mark()
+        quote = self.peek()
+        self.forward()
+        chunks.extend(self.scan_flow_scalar_non_spaces(double, start_mark))
+        while self.peek() != quote:
+            chunks.extend(self.scan_flow_scalar_spaces(double, start_mark))
+            chunks.extend(self.scan_flow_scalar_non_spaces(double, start_mark))
+        self.forward()
+        end_mark = self.get_mark()
+        return ScalarToken(''.join(chunks), False, start_mark, end_mark,
+                style)
+
+    ESCAPE_REPLACEMENTS = {
+        '0':    '\0',
+        'a':    '\x07',
+        'b':    '\x08',
+        't':    '\x09',
+        '\t':   '\x09',
+        'n':    '\x0A',
+        'v':    '\x0B',
+        'f':    '\x0C',
+        'r':    '\x0D',
+        'e':    '\x1B',
+        ' ':    '\x20',
+        '\"':   '\"',
+        '\\':   '\\',
         '/':    '/',
-        'N':    '\x85', 
-        '_':    '\xA0', 
-        'L':    '\u2028', 
-        'P':    '\u2029', 
-    } 
- 
-    ESCAPE_CODES = { 
-        'x':    2, 
-        'u':    4, 
-        'U':    8, 
-    } 
- 
-    def scan_flow_scalar_non_spaces(self, double, start_mark): 
-        # See the specification for details. 
-        chunks = [] 
-        while True: 
-            length = 0 
-            while self.peek(length) not in '\'\"\\\0 \t\r\n\x85\u2028\u2029': 
-                length += 1 
-            if length: 
-                chunks.append(self.prefix(length)) 
-                self.forward(length) 
-            ch = self.peek() 
-            if not double and ch == '\'' and self.peek(1) == '\'': 
-                chunks.append('\'') 
-                self.forward(2) 
-            elif (double and ch == '\'') or (not double and ch in '\"\\'): 
-                chunks.append(ch) 
-                self.forward() 
-            elif double and ch == '\\': 
-                self.forward() 
-                ch = self.peek() 
-                if ch in self.ESCAPE_REPLACEMENTS: 
-                    chunks.append(self.ESCAPE_REPLACEMENTS[ch]) 
-                    self.forward() 
-                elif ch in self.ESCAPE_CODES: 
-                    length = self.ESCAPE_CODES[ch] 
-                    self.forward() 
-                    for k in range(length): 
-                        if self.peek(k) not in '0123456789ABCDEFabcdef': 
-                            raise ScannerError("while scanning a double-quoted scalar", start_mark, 
-                                    "expected escape sequence of %d hexdecimal numbers, but found %r" % 
-                                        (length, self.peek(k)), self.get_mark()) 
-                    code = int(self.prefix(length), 16) 
-                    chunks.append(chr(code)) 
-                    self.forward(length) 
-                elif ch in '\r\n\x85\u2028\u2029': 
-                    self.scan_line_break() 
-                    chunks.extend(self.scan_flow_scalar_breaks(double, start_mark)) 
-                else: 
-                    raise ScannerError("while scanning a double-quoted scalar", start_mark, 
-                            "found unknown escape character %r" % ch, self.get_mark()) 
-            else: 
-                return chunks 
- 
-    def scan_flow_scalar_spaces(self, double, start_mark): 
-        # See the specification for details. 
-        chunks = [] 
-        length = 0 
-        while self.peek(length) in ' \t': 
-            length += 1 
-        whitespaces = self.prefix(length) 
-        self.forward(length) 
-        ch = self.peek() 
-        if ch == '\0': 
-            raise ScannerError("while scanning a quoted scalar", start_mark, 
-                    "found unexpected end of stream", self.get_mark()) 
-        elif ch in '\r\n\x85\u2028\u2029': 
-            line_break = self.scan_line_break() 
-            breaks = self.scan_flow_scalar_breaks(double, start_mark) 
-            if line_break != '\n': 
-                chunks.append(line_break) 
-            elif not breaks: 
-                chunks.append(' ') 
-            chunks.extend(breaks) 
-        else: 
-            chunks.append(whitespaces) 
-        return chunks 
- 
-    def scan_flow_scalar_breaks(self, double, start_mark): 
-        # See the specification for details. 
-        chunks = [] 
-        while True: 
-            # Instead of checking indentation, we check for document 
-            # separators. 
-            prefix = self.prefix(3) 
-            if (prefix == '---' or prefix == '...')   \ 
-                    and self.peek(3) in '\0 \t\r\n\x85\u2028\u2029': 
-                raise ScannerError("while scanning a quoted scalar", start_mark, 
-                        "found unexpected document separator", self.get_mark()) 
-            while self.peek() in ' \t': 
-                self.forward() 
-            if self.peek() in '\r\n\x85\u2028\u2029': 
-                chunks.append(self.scan_line_break()) 
-            else: 
-                return chunks 
- 
-    def scan_plain(self): 
-        # See the specification for details. 
-        # We add an additional restriction for the flow context: 
+        'N':    '\x85',
+        '_':    '\xA0',
+        'L':    '\u2028',
+        'P':    '\u2029',
+    }
+
+    ESCAPE_CODES = {
+        'x':    2,
+        'u':    4,
+        'U':    8,
+    }
+
+    def scan_flow_scalar_non_spaces(self, double, start_mark):
+        # See the specification for details.
+        chunks = []
+        while True:
+            length = 0
+            while self.peek(length) not in '\'\"\\\0 \t\r\n\x85\u2028\u2029':
+                length += 1
+            if length:
+                chunks.append(self.prefix(length))
+                self.forward(length)
+            ch = self.peek()
+            if not double and ch == '\'' and self.peek(1) == '\'':
+                chunks.append('\'')
+                self.forward(2)
+            elif (double and ch == '\'') or (not double and ch in '\"\\'):
+                chunks.append(ch)
+                self.forward()
+            elif double and ch == '\\':
+                self.forward()
+                ch = self.peek()
+                if ch in self.ESCAPE_REPLACEMENTS:
+                    chunks.append(self.ESCAPE_REPLACEMENTS[ch])
+                    self.forward()
+                elif ch in self.ESCAPE_CODES:
+                    length = self.ESCAPE_CODES[ch]
+                    self.forward()
+                    for k in range(length):
+                        if self.peek(k) not in '0123456789ABCDEFabcdef':
+                            raise ScannerError("while scanning a double-quoted scalar", start_mark,
+                                    "expected escape sequence of %d hexdecimal numbers, but found %r" %
+                                        (length, self.peek(k)), self.get_mark())
+                    code = int(self.prefix(length), 16)
+                    chunks.append(chr(code))
+                    self.forward(length)
+                elif ch in '\r\n\x85\u2028\u2029':
+                    self.scan_line_break()
+                    chunks.extend(self.scan_flow_scalar_breaks(double, start_mark))
+                else:
+                    raise ScannerError("while scanning a double-quoted scalar", start_mark,
+                            "found unknown escape character %r" % ch, self.get_mark())
+            else:
+                return chunks
+
+    def scan_flow_scalar_spaces(self, double, start_mark):
+        # See the specification for details.
+        chunks = []
+        length = 0
+        while self.peek(length) in ' \t':
+            length += 1
+        whitespaces = self.prefix(length)
+        self.forward(length)
+        ch = self.peek()
+        if ch == '\0':
+            raise ScannerError("while scanning a quoted scalar", start_mark,
+                    "found unexpected end of stream", self.get_mark())
+        elif ch in '\r\n\x85\u2028\u2029':
+            line_break = self.scan_line_break()
+            breaks = self.scan_flow_scalar_breaks(double, start_mark)
+            if line_break != '\n':
+                chunks.append(line_break)
+            elif not breaks:
+                chunks.append(' ')
+            chunks.extend(breaks)
+        else:
+            chunks.append(whitespaces)
+        return chunks
+
+    def scan_flow_scalar_breaks(self, double, start_mark):
+        # See the specification for details.
+        chunks = []
+        while True:
+            # Instead of checking indentation, we check for document
+            # separators.
+            prefix = self.prefix(3)
+            if (prefix == '---' or prefix == '...')   \
+                    and self.peek(3) in '\0 \t\r\n\x85\u2028\u2029':
+                raise ScannerError("while scanning a quoted scalar", start_mark,
+                        "found unexpected document separator", self.get_mark())
+            while self.peek() in ' \t':
+                self.forward()
+            if self.peek() in '\r\n\x85\u2028\u2029':
+                chunks.append(self.scan_line_break())
+            else:
+                return chunks
+
+    def scan_plain(self):
+        # See the specification for details.
+        # We add an additional restriction for the flow context:
         #   plain scalars in the flow context cannot contain ',' or '?'.
-        # We also keep track of the `allow_simple_key` flag here. 
-        # Indentation rules are loosed for the flow context. 
-        chunks = [] 
-        start_mark = self.get_mark() 
-        end_mark = start_mark 
-        indent = self.indent+1 
-        # We allow zero indentation for scalars, but then we need to check for 
-        # document separators at the beginning of the line. 
-        #if indent == 0: 
-        #    indent = 1 
-        spaces = [] 
-        while True: 
-            length = 0 
-            if self.peek() == '#': 
-                break 
-            while True: 
-                ch = self.peek(length) 
-                if ch in '\0 \t\r\n\x85\u2028\u2029'    \ 
+        # We also keep track of the `allow_simple_key` flag here.
+        # Indentation rules are loosed for the flow context.
+        chunks = []
+        start_mark = self.get_mark()
+        end_mark = start_mark
+        indent = self.indent+1
+        # We allow zero indentation for scalars, but then we need to check for
+        # document separators at the beginning of the line.
+        #if indent == 0:
+        #    indent = 1
+        spaces = []
+        while True:
+            length = 0
+            if self.peek() == '#':
+                break
+            while True:
+                ch = self.peek(length)
+                if ch in '\0 \t\r\n\x85\u2028\u2029'    \
                         or (ch == ':' and
                                 self.peek(length+1) in '\0 \t\r\n\x85\u2028\u2029'
                                       + (u',[]{}' if self.flow_level else u''))\
                         or (self.flow_level and ch in ',?[]{}'):
-                    break 
-                length += 1 
-            if length == 0: 
-                break 
-            self.allow_simple_key = False 
-            chunks.extend(spaces) 
-            chunks.append(self.prefix(length)) 
-            self.forward(length) 
-            end_mark = self.get_mark() 
-            spaces = self.scan_plain_spaces(indent, start_mark) 
-            if not spaces or self.peek() == '#' \ 
-                    or (not self.flow_level and self.column < indent): 
-                break 
-        return ScalarToken(''.join(chunks), True, start_mark, end_mark) 
- 
-    def scan_plain_spaces(self, indent, start_mark): 
-        # See the specification for details. 
-        # The specification is really confusing about tabs in plain scalars. 
-        # We just forbid them completely. Do not use tabs in YAML! 
-        chunks = [] 
-        length = 0 
-        while self.peek(length) in ' ': 
-            length += 1 
-        whitespaces = self.prefix(length) 
-        self.forward(length) 
-        ch = self.peek() 
-        if ch in '\r\n\x85\u2028\u2029': 
-            line_break = self.scan_line_break() 
-            self.allow_simple_key = True 
-            prefix = self.prefix(3) 
-            if (prefix == '---' or prefix == '...')   \ 
-                    and self.peek(3) in '\0 \t\r\n\x85\u2028\u2029': 
-                return 
-            breaks = [] 
-            while self.peek() in ' \r\n\x85\u2028\u2029': 
-                if self.peek() == ' ': 
-                    self.forward() 
-                else: 
-                    breaks.append(self.scan_line_break()) 
-                    prefix = self.prefix(3) 
-                    if (prefix == '---' or prefix == '...')   \ 
-                            and self.peek(3) in '\0 \t\r\n\x85\u2028\u2029': 
-                        return 
-            if line_break != '\n': 
-                chunks.append(line_break) 
-            elif not breaks: 
-                chunks.append(' ') 
-            chunks.extend(breaks) 
-        elif whitespaces: 
-            chunks.append(whitespaces) 
-        return chunks 
- 
-    def scan_tag_handle(self, name, start_mark): 
-        # See the specification for details. 
-        # For some strange reasons, the specification does not allow '_' in 
-        # tag handles. I have allowed it anyway. 
-        ch = self.peek() 
-        if ch != '!': 
-            raise ScannerError("while scanning a %s" % name, start_mark, 
-                    "expected '!', but found %r" % ch, self.get_mark()) 
-        length = 1 
-        ch = self.peek(length) 
-        if ch != ' ': 
-            while '0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z'  \ 
-                    or ch in '-_': 
-                length += 1 
-                ch = self.peek(length) 
-            if ch != '!': 
-                self.forward(length) 
-                raise ScannerError("while scanning a %s" % name, start_mark, 
-                        "expected '!', but found %r" % ch, self.get_mark()) 
-            length += 1 
-        value = self.prefix(length) 
-        self.forward(length) 
-        return value 
- 
-    def scan_tag_uri(self, name, start_mark): 
-        # See the specification for details. 
-        # Note: we do not check if URI is well-formed. 
-        chunks = [] 
-        length = 0 
-        ch = self.peek(length) 
-        while '0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z'  \ 
-                or ch in '-;/?:@&=+$,_.!~*\'()[]%': 
-            if ch == '%': 
-                chunks.append(self.prefix(length)) 
-                self.forward(length) 
-                length = 0 
-                chunks.append(self.scan_uri_escapes(name, start_mark)) 
-            else: 
-                length += 1 
-            ch = self.peek(length) 
-        if length: 
-            chunks.append(self.prefix(length)) 
-            self.forward(length) 
-            length = 0 
-        if not chunks: 
-            raise ScannerError("while parsing a %s" % name, start_mark, 
-                    "expected URI, but found %r" % ch, self.get_mark()) 
-        return ''.join(chunks) 
- 
-    def scan_uri_escapes(self, name, start_mark): 
-        # See the specification for details. 
-        codes = [] 
-        mark = self.get_mark() 
-        while self.peek() == '%': 
-            self.forward() 
-            for k in range(2): 
-                if self.peek(k) not in '0123456789ABCDEFabcdef': 
-                    raise ScannerError("while scanning a %s" % name, start_mark, 
-                            "expected URI escape sequence of 2 hexdecimal numbers, but found %r" 
-                            % self.peek(k), self.get_mark()) 
-            codes.append(int(self.prefix(2), 16)) 
-            self.forward(2) 
-        try: 
-            value = bytes(codes).decode('utf-8') 
-        except UnicodeDecodeError as exc: 
-            raise ScannerError("while scanning a %s" % name, start_mark, str(exc), mark) 
-        return value 
- 
-    def scan_line_break(self): 
-        # Transforms: 
-        #   '\r\n'      :   '\n' 
-        #   '\r'        :   '\n' 
-        #   '\n'        :   '\n' 
-        #   '\x85'      :   '\n' 
-        #   '\u2028'    :   '\u2028' 
-        #   '\u2029     :   '\u2029' 
-        #   default     :   '' 
-        ch = self.peek() 
-        if ch in '\r\n\x85': 
-            if self.prefix(2) == '\r\n': 
-                self.forward(2) 
-            else: 
-                self.forward() 
-            return '\n' 
-        elif ch in '\u2028\u2029': 
-            self.forward() 
-            return ch 
-        return '' 
+                    break
+                length += 1
+            if length == 0:
+                break
+            self.allow_simple_key = False
+            chunks.extend(spaces)
+            chunks.append(self.prefix(length))
+            self.forward(length)
+            end_mark = self.get_mark()
+            spaces = self.scan_plain_spaces(indent, start_mark)
+            if not spaces or self.peek() == '#' \
+                    or (not self.flow_level and self.column < indent):
+                break
+        return ScalarToken(''.join(chunks), True, start_mark, end_mark)
+
+    def scan_plain_spaces(self, indent, start_mark):
+        # See the specification for details.
+        # The specification is really confusing about tabs in plain scalars.
+        # We just forbid them completely. Do not use tabs in YAML!
+        chunks = []
+        length = 0
+        while self.peek(length) in ' ':
+            length += 1
+        whitespaces = self.prefix(length)
+        self.forward(length)
+        ch = self.peek()
+        if ch in '\r\n\x85\u2028\u2029':
+            line_break = self.scan_line_break()
+            self.allow_simple_key = True
+            prefix = self.prefix(3)
+            if (prefix == '---' or prefix == '...')   \
+                    and self.peek(3) in '\0 \t\r\n\x85\u2028\u2029':
+                return
+            breaks = []
+            while self.peek() in ' \r\n\x85\u2028\u2029':
+                if self.peek() == ' ':
+                    self.forward()
+                else:
+                    breaks.append(self.scan_line_break())
+                    prefix = self.prefix(3)
+                    if (prefix == '---' or prefix == '...')   \
+                            and self.peek(3) in '\0 \t\r\n\x85\u2028\u2029':
+                        return
+            if line_break != '\n':
+                chunks.append(line_break)
+            elif not breaks:
+                chunks.append(' ')
+            chunks.extend(breaks)
+        elif whitespaces:
+            chunks.append(whitespaces)
+        return chunks
+
+    def scan_tag_handle(self, name, start_mark):
+        # See the specification for details.
+        # For some strange reasons, the specification does not allow '_' in
+        # tag handles. I have allowed it anyway.
+        ch = self.peek()
+        if ch != '!':
+            raise ScannerError("while scanning a %s" % name, start_mark,
+                    "expected '!', but found %r" % ch, self.get_mark())
+        length = 1
+        ch = self.peek(length)
+        if ch != ' ':
+            while '0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z'  \
+                    or ch in '-_':
+                length += 1
+                ch = self.peek(length)
+            if ch != '!':
+                self.forward(length)
+                raise ScannerError("while scanning a %s" % name, start_mark,
+                        "expected '!', but found %r" % ch, self.get_mark())
+            length += 1
+        value = self.prefix(length)
+        self.forward(length)
+        return value
+
+    def scan_tag_uri(self, name, start_mark):
+        # See the specification for details.
+        # Note: we do not check if URI is well-formed.
+        chunks = []
+        length = 0
+        ch = self.peek(length)
+        while '0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z'  \
+                or ch in '-;/?:@&=+$,_.!~*\'()[]%':
+            if ch == '%':
+                chunks.append(self.prefix(length))
+                self.forward(length)
+                length = 0
+                chunks.append(self.scan_uri_escapes(name, start_mark))
+            else:
+                length += 1
+            ch = self.peek(length)
+        if length:
+            chunks.append(self.prefix(length))
+            self.forward(length)
+            length = 0
+        if not chunks:
+            raise ScannerError("while parsing a %s" % name, start_mark,
+                    "expected URI, but found %r" % ch, self.get_mark())
+        return ''.join(chunks)
+
+    def scan_uri_escapes(self, name, start_mark):
+        # See the specification for details.
+        codes = []
+        mark = self.get_mark()
+        while self.peek() == '%':
+            self.forward()
+            for k in range(2):
+                if self.peek(k) not in '0123456789ABCDEFabcdef':
+                    raise ScannerError("while scanning a %s" % name, start_mark,
+                            "expected URI escape sequence of 2 hexdecimal numbers, but found %r"
+                            % self.peek(k), self.get_mark())
+            codes.append(int(self.prefix(2), 16))
+            self.forward(2)
+        try:
+            value = bytes(codes).decode('utf-8')
+        except UnicodeDecodeError as exc:
+            raise ScannerError("while scanning a %s" % name, start_mark, str(exc), mark)
+        return value
+
+    def scan_line_break(self):
+        # Transforms:
+        #   '\r\n'      :   '\n'
+        #   '\r'        :   '\n'
+        #   '\n'        :   '\n'
+        #   '\x85'      :   '\n'
+        #   '\u2028'    :   '\u2028'
+        #   '\u2029     :   '\u2029'
+        #   default     :   ''
+        ch = self.peek()
+        if ch in '\r\n\x85':
+            if self.prefix(2) == '\r\n':
+                self.forward(2)
+            else:
+                self.forward()
+            return '\n'
+        elif ch in '\u2028\u2029':
+            self.forward()
+            return ch
+        return ''
diff --git a/contrib/python/PyYAML/py3/yaml/serializer.py b/contrib/python/PyYAML/py3/yaml/serializer.py
index 6f18f68ad4..fe911e67ae 100644
--- a/contrib/python/PyYAML/py3/yaml/serializer.py
+++ b/contrib/python/PyYAML/py3/yaml/serializer.py
@@ -1,111 +1,111 @@
- 
-__all__ = ['Serializer', 'SerializerError'] 
- 
-from .error import YAMLError 
-from .events import * 
-from .nodes import * 
- 
-class SerializerError(YAMLError): 
-    pass 
- 
-class Serializer: 
- 
-    ANCHOR_TEMPLATE = 'id%03d' 
- 
-    def __init__(self, encoding=None, 
-            explicit_start=None, explicit_end=None, version=None, tags=None): 
-        self.use_encoding = encoding 
-        self.use_explicit_start = explicit_start 
-        self.use_explicit_end = explicit_end 
-        self.use_version = version 
-        self.use_tags = tags 
-        self.serialized_nodes = {} 
-        self.anchors = {} 
-        self.last_anchor_id = 0 
-        self.closed = None 
- 
-    def open(self): 
-        if self.closed is None: 
-            self.emit(StreamStartEvent(encoding=self.use_encoding)) 
-            self.closed = False 
-        elif self.closed: 
-            raise SerializerError("serializer is closed") 
-        else: 
-            raise SerializerError("serializer is already opened") 
- 
-    def close(self): 
-        if self.closed is None: 
-            raise SerializerError("serializer is not opened") 
-        elif not self.closed: 
-            self.emit(StreamEndEvent()) 
-            self.closed = True 
- 
-    #def __del__(self): 
-    #    self.close() 
- 
-    def serialize(self, node): 
-        if self.closed is None: 
-            raise SerializerError("serializer is not opened") 
-        elif self.closed: 
-            raise SerializerError("serializer is closed") 
-        self.emit(DocumentStartEvent(explicit=self.use_explicit_start, 
-            version=self.use_version, tags=self.use_tags)) 
-        self.anchor_node(node) 
-        self.serialize_node(node, None, None) 
-        self.emit(DocumentEndEvent(explicit=self.use_explicit_end)) 
-        self.serialized_nodes = {} 
-        self.anchors = {} 
-        self.last_anchor_id = 0 
- 
-    def anchor_node(self, node): 
-        if node in self.anchors: 
-            if self.anchors[node] is None: 
-                self.anchors[node] = self.generate_anchor(node) 
-        else: 
-            self.anchors[node] = None 
-            if isinstance(node, SequenceNode): 
-                for item in node.value: 
-                    self.anchor_node(item) 
-            elif isinstance(node, MappingNode): 
-                for key, value in node.value: 
-                    self.anchor_node(key) 
-                    self.anchor_node(value) 
- 
-    def generate_anchor(self, node): 
-        self.last_anchor_id += 1 
-        return self.ANCHOR_TEMPLATE % self.last_anchor_id 
- 
-    def serialize_node(self, node, parent, index): 
-        alias = self.anchors[node] 
-        if node in self.serialized_nodes: 
-            self.emit(AliasEvent(alias)) 
-        else: 
-            self.serialized_nodes[node] = True 
-            self.descend_resolver(parent, index) 
-            if isinstance(node, ScalarNode): 
-                detected_tag = self.resolve(ScalarNode, node.value, (True, False)) 
-                default_tag = self.resolve(ScalarNode, node.value, (False, True)) 
-                implicit = (node.tag == detected_tag), (node.tag == default_tag) 
-                self.emit(ScalarEvent(alias, node.tag, implicit, node.value, 
-                    style=node.style)) 
-            elif isinstance(node, SequenceNode): 
-                implicit = (node.tag 
-                            == self.resolve(SequenceNode, node.value, True)) 
-                self.emit(SequenceStartEvent(alias, node.tag, implicit, 
-                    flow_style=node.flow_style)) 
-                index = 0 
-                for item in node.value: 
-                    self.serialize_node(item, node, index) 
-                    index += 1 
-                self.emit(SequenceEndEvent()) 
-            elif isinstance(node, MappingNode): 
-                implicit = (node.tag 
-                            == self.resolve(MappingNode, node.value, True)) 
-                self.emit(MappingStartEvent(alias, node.tag, implicit, 
-                    flow_style=node.flow_style)) 
-                for key, value in node.value: 
-                    self.serialize_node(key, node, None) 
-                    self.serialize_node(value, node, key) 
-                self.emit(MappingEndEvent()) 
-            self.ascend_resolver() 
- 
+
+__all__ = ['Serializer', 'SerializerError']
+
+from .error import YAMLError
+from .events import *
+from .nodes import *
+
+class SerializerError(YAMLError):
+    pass
+
+class Serializer:
+
+    ANCHOR_TEMPLATE = 'id%03d'
+
+    def __init__(self, encoding=None,
+            explicit_start=None, explicit_end=None, version=None, tags=None):
+        self.use_encoding = encoding
+        self.use_explicit_start = explicit_start
+        self.use_explicit_end = explicit_end
+        self.use_version = version
+        self.use_tags = tags
+        self.serialized_nodes = {}
+        self.anchors = {}
+        self.last_anchor_id = 0
+        self.closed = None
+
+    def open(self):
+        if self.closed is None:
+            self.emit(StreamStartEvent(encoding=self.use_encoding))
+            self.closed = False
+        elif self.closed:
+            raise SerializerError("serializer is closed")
+        else:
+            raise SerializerError("serializer is already opened")
+
+    def close(self):
+        if self.closed is None:
+            raise SerializerError("serializer is not opened")
+        elif not self.closed:
+            self.emit(StreamEndEvent())
+            self.closed = True
+
+    #def __del__(self):
+    #    self.close()
+
+    def serialize(self, node):
+        if self.closed is None:
+            raise SerializerError("serializer is not opened")
+        elif self.closed:
+            raise SerializerError("serializer is closed")
+        self.emit(DocumentStartEvent(explicit=self.use_explicit_start,
+            version=self.use_version, tags=self.use_tags))
+        self.anchor_node(node)
+        self.serialize_node(node, None, None)
+        self.emit(DocumentEndEvent(explicit=self.use_explicit_end))
+        self.serialized_nodes = {}
+        self.anchors = {}
+        self.last_anchor_id = 0
+
+    def anchor_node(self, node):
+        if node in self.anchors:
+            if self.anchors[node] is None:
+                self.anchors[node] = self.generate_anchor(node)
+        else:
+            self.anchors[node] = None
+            if isinstance(node, SequenceNode):
+                for item in node.value:
+                    self.anchor_node(item)
+            elif isinstance(node, MappingNode):
+                for key, value in node.value:
+                    self.anchor_node(key)
+                    self.anchor_node(value)
+
+    def generate_anchor(self, node):
+        self.last_anchor_id += 1
+        return self.ANCHOR_TEMPLATE % self.last_anchor_id
+
+    def serialize_node(self, node, parent, index):
+        alias = self.anchors[node]
+        if node in self.serialized_nodes:
+            self.emit(AliasEvent(alias))
+        else:
+            self.serialized_nodes[node] = True
+            self.descend_resolver(parent, index)
+            if isinstance(node, ScalarNode):
+                detected_tag = self.resolve(ScalarNode, node.value, (True, False))
+                default_tag = self.resolve(ScalarNode, node.value, (False, True))
+                implicit = (node.tag == detected_tag), (node.tag == default_tag)
+                self.emit(ScalarEvent(alias, node.tag, implicit, node.value,
+                    style=node.style))
+            elif isinstance(node, SequenceNode):
+                implicit = (node.tag
+                            == self.resolve(SequenceNode, node.value, True))
+                self.emit(SequenceStartEvent(alias, node.tag, implicit,
+                    flow_style=node.flow_style))
+                index = 0
+                for item in node.value:
+                    self.serialize_node(item, node, index)
+                    index += 1
+                self.emit(SequenceEndEvent())
+            elif isinstance(node, MappingNode):
+                implicit = (node.tag
+                            == self.resolve(MappingNode, node.value, True))
+                self.emit(MappingStartEvent(alias, node.tag, implicit,
+                    flow_style=node.flow_style))
+                for key, value in node.value:
+                    self.serialize_node(key, node, None)
+                    self.serialize_node(value, node, key)
+                self.emit(MappingEndEvent())
+            self.ascend_resolver()
+
diff --git a/contrib/python/PyYAML/py3/yaml/tokens.py b/contrib/python/PyYAML/py3/yaml/tokens.py
index 34da1025dd..4d0b48a394 100644
--- a/contrib/python/PyYAML/py3/yaml/tokens.py
+++ b/contrib/python/PyYAML/py3/yaml/tokens.py
@@ -1,104 +1,104 @@
- 
-class Token(object): 
-    def __init__(self, start_mark, end_mark): 
-        self.start_mark = start_mark 
-        self.end_mark = end_mark 
-    def __repr__(self): 
-        attributes = [key for key in self.__dict__ 
-                if not key.endswith('_mark')] 
-        attributes.sort() 
-        arguments = ', '.join(['%s=%r' % (key, getattr(self, key)) 
-                for key in attributes]) 
-        return '%s(%s)' % (self.__class__.__name__, arguments) 
- 
-#class BOMToken(Token): 
-#    id = '<byte order mark>' 
- 
-class DirectiveToken(Token): 
-    id = '<directive>' 
-    def __init__(self, name, value, start_mark, end_mark): 
-        self.name = name 
-        self.value = value 
-        self.start_mark = start_mark 
-        self.end_mark = end_mark 
- 
-class DocumentStartToken(Token): 
-    id = '<document start>' 
- 
-class DocumentEndToken(Token): 
-    id = '<document end>' 
- 
-class StreamStartToken(Token): 
-    id = '<stream start>' 
-    def __init__(self, start_mark=None, end_mark=None, 
-            encoding=None): 
-        self.start_mark = start_mark 
-        self.end_mark = end_mark 
-        self.encoding = encoding 
- 
-class StreamEndToken(Token): 
-    id = '<stream end>' 
- 
-class BlockSequenceStartToken(Token): 
-    id = '<block sequence start>' 
- 
-class BlockMappingStartToken(Token): 
-    id = '<block mapping start>' 
- 
-class BlockEndToken(Token): 
-    id = '<block end>' 
- 
-class FlowSequenceStartToken(Token): 
-    id = '[' 
- 
-class FlowMappingStartToken(Token): 
-    id = '{' 
- 
-class FlowSequenceEndToken(Token): 
-    id = ']' 
- 
-class FlowMappingEndToken(Token): 
-    id = '}' 
- 
-class KeyToken(Token): 
-    id = '?' 
- 
-class ValueToken(Token): 
-    id = ':' 
- 
-class BlockEntryToken(Token): 
-    id = '-' 
- 
-class FlowEntryToken(Token): 
-    id = ',' 
- 
-class AliasToken(Token): 
-    id = '<alias>' 
-    def __init__(self, value, start_mark, end_mark): 
-        self.value = value 
-        self.start_mark = start_mark 
-        self.end_mark = end_mark 
- 
-class AnchorToken(Token): 
-    id = '<anchor>' 
-    def __init__(self, value, start_mark, end_mark): 
-        self.value = value 
-        self.start_mark = start_mark 
-        self.end_mark = end_mark 
- 
-class TagToken(Token): 
-    id = '<tag>' 
-    def __init__(self, value, start_mark, end_mark): 
-        self.value = value 
-        self.start_mark = start_mark 
-        self.end_mark = end_mark 
- 
-class ScalarToken(Token): 
-    id = '<scalar>' 
-    def __init__(self, value, plain, start_mark, end_mark, style=None): 
-        self.value = value 
-        self.plain = plain 
-        self.start_mark = start_mark 
-        self.end_mark = end_mark 
-        self.style = style 
- 
+
+class Token(object):
+    def __init__(self, start_mark, end_mark):
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+    def __repr__(self):
+        attributes = [key for key in self.__dict__
+                if not key.endswith('_mark')]
+        attributes.sort()
+        arguments = ', '.join(['%s=%r' % (key, getattr(self, key))
+                for key in attributes])
+        return '%s(%s)' % (self.__class__.__name__, arguments)
+
+#class BOMToken(Token):
+#    id = '<byte order mark>'
+
+class DirectiveToken(Token):
+    id = '<directive>'
+    def __init__(self, name, value, start_mark, end_mark):
+        self.name = name
+        self.value = value
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+
+class DocumentStartToken(Token):
+    id = '<document start>'
+
+class DocumentEndToken(Token):
+    id = '<document end>'
+
+class StreamStartToken(Token):
+    id = '<stream start>'
+    def __init__(self, start_mark=None, end_mark=None,
+            encoding=None):
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+        self.encoding = encoding
+
+class StreamEndToken(Token):
+    id = '<stream end>'
+
+class BlockSequenceStartToken(Token):
+    id = '<block sequence start>'
+
+class BlockMappingStartToken(Token):
+    id = '<block mapping start>'
+
+class BlockEndToken(Token):
+    id = '<block end>'
+
+class FlowSequenceStartToken(Token):
+    id = '['
+
+class FlowMappingStartToken(Token):
+    id = '{'
+
+class FlowSequenceEndToken(Token):
+    id = ']'
+
+class FlowMappingEndToken(Token):
+    id = '}'
+
+class KeyToken(Token):
+    id = '?'
+
+class ValueToken(Token):
+    id = ':'
+
+class BlockEntryToken(Token):
+    id = '-'
+
+class FlowEntryToken(Token):
+    id = ','
+
+class AliasToken(Token):
+    id = '<alias>'
+    def __init__(self, value, start_mark, end_mark):
+        self.value = value
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+
+class AnchorToken(Token):
+    id = '<anchor>'
+    def __init__(self, value, start_mark, end_mark):
+        self.value = value
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+
+class TagToken(Token):
+    id = '<tag>'
+    def __init__(self, value, start_mark, end_mark):
+        self.value = value
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+
+class ScalarToken(Token):
+    id = '<scalar>'
+    def __init__(self, value, plain, start_mark, end_mark, style=None):
+        self.value = value
+        self.plain = plain
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+        self.style = style
+
diff --git a/contrib/python/PyYAML/ya.make b/contrib/python/PyYAML/ya.make
index 5c1fd51a18..a604fce51f 100644
--- a/contrib/python/PyYAML/ya.make
+++ b/contrib/python/PyYAML/ya.make
@@ -7,11 +7,11 @@ OWNER(g:python-contrib)
 IF (PYTHON2)
     PEERDIR(
         contrib/python/PyYAML/py2
-    ) 
+    )
 ELSE()
     PEERDIR(
         contrib/python/PyYAML/py3
-    ) 
+    )
 ENDIF()
 
 NO_LINT()