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

10 files changed, 1634 insertions, 1634 deletions

diff --git a/contrib/python/attrs/attr/__init__.py b/contrib/python/attrs/attr/__init__.py
index 506199800f..b1ce7fe248 100644
--- a/contrib/python/attrs/attr/__init__.py
+++ b/contrib/python/attrs/attr/__init__.py
@@ -1,14 +1,14 @@
-from __future__ import absolute_import, division, print_function 
- 
+from __future__ import absolute_import, division, print_function
+
 import sys
 
-from functools import partial 
- 
+from functools import partial
+
 from . import converters, exceptions, filters, setters, validators
 from ._cmp import cmp_using
-from ._config import get_run_validators, set_run_validators 
+from ._config import get_run_validators, set_run_validators
 from ._funcs import asdict, assoc, astuple, evolve, has, resolve_types
-from ._make import ( 
+from ._make import (
     NOTHING,
     Attribute,
     Factory,
@@ -18,59 +18,59 @@ from ._make import (
     fields_dict,
     make_class,
     validate,
-) 
+)
 from ._version_info import VersionInfo
- 
- 
+
+
 __version__ = "21.2.0"
 __version_info__ = VersionInfo._from_version_string(__version__)
- 
-__title__ = "attrs" 
-__description__ = "Classes Without Boilerplate" 
+
+__title__ = "attrs"
+__description__ = "Classes Without Boilerplate"
 __url__ = "https://www.attrs.org/"
 __uri__ = __url__
-__doc__ = __description__ + " <" + __uri__ + ">" 
- 
-__author__ = "Hynek Schlawack" 
-__email__ = "hs@ox.cx" 
- 
-__license__ = "MIT" 
-__copyright__ = "Copyright (c) 2015 Hynek Schlawack" 
- 
- 
-s = attributes = attrs 
-ib = attr = attrib 
-dataclass = partial(attrs, auto_attribs=True)  # happy Easter ;) 
- 
-__all__ = [ 
-    "Attribute", 
-    "Factory", 
-    "NOTHING", 
-    "asdict", 
-    "assoc", 
-    "astuple", 
-    "attr", 
-    "attrib", 
-    "attributes", 
-    "attrs", 
+__doc__ = __description__ + " <" + __uri__ + ">"
+
+__author__ = "Hynek Schlawack"
+__email__ = "hs@ox.cx"
+
+__license__ = "MIT"
+__copyright__ = "Copyright (c) 2015 Hynek Schlawack"
+
+
+s = attributes = attrs
+ib = attr = attrib
+dataclass = partial(attrs, auto_attribs=True)  # happy Easter ;)
+
+__all__ = [
+    "Attribute",
+    "Factory",
+    "NOTHING",
+    "asdict",
+    "assoc",
+    "astuple",
+    "attr",
+    "attrib",
+    "attributes",
+    "attrs",
     "cmp_using",
-    "converters", 
-    "evolve", 
-    "exceptions", 
-    "fields", 
-    "fields_dict", 
-    "filters", 
-    "get_run_validators", 
-    "has", 
-    "ib", 
-    "make_class", 
+    "converters",
+    "evolve",
+    "exceptions",
+    "fields",
+    "fields_dict",
+    "filters",
+    "get_run_validators",
+    "has",
+    "ib",
+    "make_class",
     "resolve_types",
-    "s", 
-    "set_run_validators", 
+    "s",
+    "set_run_validators",
     "setters",
-    "validate", 
-    "validators", 
-] 
+    "validate",
+    "validators",
+]
 
 if sys.version_info[:2] >= (3, 6):
     from ._next_gen import define, field, frozen, mutable
diff --git a/contrib/python/attrs/attr/_compat.py b/contrib/python/attrs/attr/_compat.py
index 9fefc975e1..6939f338da 100644
--- a/contrib/python/attrs/attr/_compat.py
+++ b/contrib/python/attrs/attr/_compat.py
@@ -1,33 +1,33 @@
-from __future__ import absolute_import, division, print_function 
- 
-import platform 
-import sys 
-import types 
-import warnings 
- 
- 
-PY2 = sys.version_info[0] == 2 
-PYPY = platform.python_implementation() == "PyPy" 
- 
- 
-if PYPY or sys.version_info[:2] >= (3, 6): 
-    ordered_dict = dict 
-else: 
-    from collections import OrderedDict 
-
-    ordered_dict = OrderedDict 
- 
- 
-if PY2: 
+from __future__ import absolute_import, division, print_function
+
+import platform
+import sys
+import types
+import warnings
+
+
+PY2 = sys.version_info[0] == 2
+PYPY = platform.python_implementation() == "PyPy"
+
+
+if PYPY or sys.version_info[:2] >= (3, 6):
+    ordered_dict = dict
+else:
+    from collections import OrderedDict
+
+    ordered_dict = OrderedDict
+
+
+if PY2:
     from collections import Mapping, Sequence
- 
+
     from UserDict import IterableUserDict
 
-    # We 'bundle' isclass instead of using inspect as importing inspect is 
-    # fairly expensive (order of 10-15 ms for a modern machine in 2016) 
-    def isclass(klass): 
-        return isinstance(klass, (type, types.ClassType)) 
- 
+    # We 'bundle' isclass instead of using inspect as importing inspect is
+    # fairly expensive (order of 10-15 ms for a modern machine in 2016)
+    def isclass(klass):
+        return isinstance(klass, (type, types.ClassType))
+
     def new_class(name, bases, kwds, exec_body):
         """
         A minimal stub of types.new_class that we need for make_class.
@@ -37,69 +37,69 @@ if PY2:
 
         return type(name, bases, ns)
 
-    # TYPE is used in exceptions, repr(int) is different on Python 2 and 3. 
-    TYPE = "type" 
- 
-    def iteritems(d): 
-        return d.iteritems() 
- 
-    # Python 2 is bereft of a read-only dict proxy, so we make one! 
-    class ReadOnlyDict(IterableUserDict): 
-        """ 
-        Best-effort read-only dict wrapper. 
-        """ 
- 
-        def __setitem__(self, key, val): 
-            # We gently pretend we're a Python 3 mappingproxy. 
+    # TYPE is used in exceptions, repr(int) is different on Python 2 and 3.
+    TYPE = "type"
+
+    def iteritems(d):
+        return d.iteritems()
+
+    # Python 2 is bereft of a read-only dict proxy, so we make one!
+    class ReadOnlyDict(IterableUserDict):
+        """
+        Best-effort read-only dict wrapper.
+        """
+
+        def __setitem__(self, key, val):
+            # We gently pretend we're a Python 3 mappingproxy.
             raise TypeError(
                 "'mappingproxy' object does not support item assignment"
             )
- 
-        def update(self, _): 
-            # We gently pretend we're a Python 3 mappingproxy. 
+
+        def update(self, _):
+            # We gently pretend we're a Python 3 mappingproxy.
             raise AttributeError(
                 "'mappingproxy' object has no attribute 'update'"
             )
- 
-        def __delitem__(self, _): 
-            # We gently pretend we're a Python 3 mappingproxy. 
+
+        def __delitem__(self, _):
+            # We gently pretend we're a Python 3 mappingproxy.
             raise TypeError(
                 "'mappingproxy' object does not support item deletion"
             )
- 
-        def clear(self): 
-            # We gently pretend we're a Python 3 mappingproxy. 
+
+        def clear(self):
+            # We gently pretend we're a Python 3 mappingproxy.
             raise AttributeError(
                 "'mappingproxy' object has no attribute 'clear'"
             )
- 
-        def pop(self, key, default=None): 
-            # We gently pretend we're a Python 3 mappingproxy. 
+
+        def pop(self, key, default=None):
+            # We gently pretend we're a Python 3 mappingproxy.
             raise AttributeError(
                 "'mappingproxy' object has no attribute 'pop'"
             )
- 
-        def popitem(self): 
-            # We gently pretend we're a Python 3 mappingproxy. 
+
+        def popitem(self):
+            # We gently pretend we're a Python 3 mappingproxy.
             raise AttributeError(
                 "'mappingproxy' object has no attribute 'popitem'"
             )
- 
-        def setdefault(self, key, default=None): 
-            # We gently pretend we're a Python 3 mappingproxy. 
+
+        def setdefault(self, key, default=None):
+            # We gently pretend we're a Python 3 mappingproxy.
             raise AttributeError(
                 "'mappingproxy' object has no attribute 'setdefault'"
             )
- 
-        def __repr__(self): 
-            # Override to be identical to the Python 3 version. 
-            return "mappingproxy(" + repr(self.data) + ")" 
- 
-    def metadata_proxy(d): 
-        res = ReadOnlyDict() 
-        res.data.update(d)  # We blocked update, so we have to do it like this. 
-        return res 
- 
+
+        def __repr__(self):
+            # Override to be identical to the Python 3 version.
+            return "mappingproxy(" + repr(self.data) + ")"
+
+    def metadata_proxy(d):
+        res = ReadOnlyDict()
+        res.data.update(d)  # We blocked update, so we have to do it like this.
+        return res
+
     def just_warn(*args, **kw):  # pragma: no cover
         """
         We only warn on Python 3 because we are not aware of any concrete
@@ -123,30 +123,30 @@ else:  # Python 3 and later.
             stacklevel=2,
         )
 
-    def isclass(klass): 
-        return isinstance(klass, type) 
- 
-    TYPE = "class" 
- 
-    def iteritems(d): 
-        return d.items() 
- 
+    def isclass(klass):
+        return isinstance(klass, type)
+
+    TYPE = "class"
+
+    def iteritems(d):
+        return d.items()
+
     new_class = types.new_class
 
-    def metadata_proxy(d): 
-        return types.MappingProxyType(dict(d)) 
- 
- 
-def make_set_closure_cell(): 
+    def metadata_proxy(d):
+        return types.MappingProxyType(dict(d))
+
+
+def make_set_closure_cell():
     """Return a function of two arguments (cell, value) which sets
     the value stored in the closure cell `cell` to `value`.
-    """ 
+    """
     # pypy makes this easy. (It also supports the logic below, but
     # why not do the easy/fast thing?)
     if PYPY:
 
-        def set_closure_cell(cell, value): 
-            cell.__setstate__((value,)) 
+        def set_closure_cell(cell, value):
+            cell.__setstate__((value,))
 
         return set_closure_cell
 
@@ -235,8 +235,8 @@ def make_set_closure_cell():
 
     except Exception:
         return just_warn
-    else: 
+    else:
         return set_closure_cell
- 
- 
-set_closure_cell = make_set_closure_cell() 
+
+
+set_closure_cell = make_set_closure_cell()
diff --git a/contrib/python/attrs/attr/_config.py b/contrib/python/attrs/attr/_config.py
index 13923f3998..8ec920962d 100644
--- a/contrib/python/attrs/attr/_config.py
+++ b/contrib/python/attrs/attr/_config.py
@@ -1,23 +1,23 @@
-from __future__ import absolute_import, division, print_function 
- 
- 
-__all__ = ["set_run_validators", "get_run_validators"] 
- 
-_run_validators = True 
- 
- 
-def set_run_validators(run): 
-    """ 
-    Set whether or not validators are run.  By default, they are run. 
-    """ 
-    if not isinstance(run, bool): 
-        raise TypeError("'run' must be bool.") 
-    global _run_validators 
-    _run_validators = run 
- 
- 
-def get_run_validators(): 
-    """ 
-    Return whether or not validators are run. 
-    """ 
-    return _run_validators 
+from __future__ import absolute_import, division, print_function
+
+
+__all__ = ["set_run_validators", "get_run_validators"]
+
+_run_validators = True
+
+
+def set_run_validators(run):
+    """
+    Set whether or not validators are run.  By default, they are run.
+    """
+    if not isinstance(run, bool):
+        raise TypeError("'run' must be bool.")
+    global _run_validators
+    _run_validators = run
+
+
+def get_run_validators():
+    """
+    Return whether or not validators are run.
+    """
+    return _run_validators
diff --git a/contrib/python/attrs/attr/_funcs.py b/contrib/python/attrs/attr/_funcs.py
index 27487844af..fda508c5c4 100644
--- a/contrib/python/attrs/attr/_funcs.py
+++ b/contrib/python/attrs/attr/_funcs.py
@@ -1,12 +1,12 @@
-from __future__ import absolute_import, division, print_function 
- 
-import copy 
- 
-from ._compat import iteritems 
-from ._make import NOTHING, _obj_setattr, fields 
-from .exceptions import AttrsAttributeNotFoundError 
- 
- 
+from __future__ import absolute_import, division, print_function
+
+import copy
+
+from ._compat import iteritems
+from ._make import NOTHING, _obj_setattr, fields
+from .exceptions import AttrsAttributeNotFoundError
+
+
 def asdict(
     inst,
     recurse=True,
@@ -15,50 +15,50 @@ def asdict(
     retain_collection_types=False,
     value_serializer=None,
 ):
-    """ 
-    Return the ``attrs`` attribute values of *inst* as a dict. 
- 
-    Optionally recurse into other ``attrs``-decorated classes. 
- 
-    :param inst: Instance of an ``attrs``-decorated class. 
-    :param bool recurse: Recurse into classes that are also 
-        ``attrs``-decorated. 
-    :param callable filter: A callable whose return code determines whether an 
-        attribute or element is included (``True``) or dropped (``False``).  Is 
+    """
+    Return the ``attrs`` attribute values of *inst* as a dict.
+
+    Optionally recurse into other ``attrs``-decorated classes.
+
+    :param inst: Instance of an ``attrs``-decorated class.
+    :param bool recurse: Recurse into classes that are also
+        ``attrs``-decorated.
+    :param callable filter: A callable whose return code determines whether an
+        attribute or element is included (``True``) or dropped (``False``).  Is
         called with the `attr.Attribute` as the first argument and the
-        value as the second argument. 
-    :param callable dict_factory: A callable to produce dictionaries from.  For 
-        example, to produce ordered dictionaries instead of normal Python 
-        dictionaries, pass in ``collections.OrderedDict``. 
-    :param bool retain_collection_types: Do not convert to ``list`` when 
-        encountering an attribute whose type is ``tuple`` or ``set``.  Only 
-        meaningful if ``recurse`` is ``True``. 
+        value as the second argument.
+    :param callable dict_factory: A callable to produce dictionaries from.  For
+        example, to produce ordered dictionaries instead of normal Python
+        dictionaries, pass in ``collections.OrderedDict``.
+    :param bool retain_collection_types: Do not convert to ``list`` when
+        encountering an attribute whose type is ``tuple`` or ``set``.  Only
+        meaningful if ``recurse`` is ``True``.
     :param Optional[callable] value_serializer: A hook that is called for every
         attribute or dict key/value.  It receives the current instance, field
         and value and must return the (updated) value.  The hook is run *after*
         the optional *filter* has been applied.
- 
-    :rtype: return type of *dict_factory* 
- 
-    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs`` 
-        class. 
- 
-    ..  versionadded:: 16.0.0 *dict_factory* 
-    ..  versionadded:: 16.1.0 *retain_collection_types* 
+
+    :rtype: return type of *dict_factory*
+
+    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
+        class.
+
+    ..  versionadded:: 16.0.0 *dict_factory*
+    ..  versionadded:: 16.1.0 *retain_collection_types*
     ..  versionadded:: 20.3.0 *value_serializer*
-    """ 
-    attrs = fields(inst.__class__) 
-    rv = dict_factory() 
-    for a in attrs: 
-        v = getattr(inst, a.name) 
-        if filter is not None and not filter(a, v): 
-            continue 
+    """
+    attrs = fields(inst.__class__)
+    rv = dict_factory()
+    for a in attrs:
+        v = getattr(inst, a.name)
+        if filter is not None and not filter(a, v):
+            continue
 
         if value_serializer is not None:
             v = value_serializer(inst, a, v)
 
-        if recurse is True: 
-            if has(v.__class__): 
+        if recurse is True:
+            if has(v.__class__):
                 rv[a.name] = asdict(
                     v,
                     True,
@@ -68,7 +68,7 @@ def asdict(
                     value_serializer,
                 )
             elif isinstance(v, (tuple, list, set, frozenset)):
-                cf = v.__class__ if retain_collection_types is True else list 
+                cf = v.__class__ if retain_collection_types is True else list
                 rv[a.name] = cf(
                     [
                         _asdict_anything(
@@ -81,8 +81,8 @@ def asdict(
                         for i in v
                     ]
                 )
-            elif isinstance(v, dict): 
-                df = dict_factory 
+            elif isinstance(v, dict):
+                df = dict_factory
                 rv[a.name] = df(
                     (
                         _asdict_anything(
@@ -102,13 +102,13 @@ def asdict(
                     )
                     for kk, vv in iteritems(v)
                 )
-            else: 
-                rv[a.name] = v 
-        else: 
-            rv[a.name] = v 
-    return rv 
- 
- 
+            else:
+                rv[a.name] = v
+        else:
+            rv[a.name] = v
+    return rv
+
+
 def _asdict_anything(
     val,
     filter,
@@ -116,7 +116,7 @@ def _asdict_anything(
     retain_collection_types,
     value_serializer,
 ):
-    """ 
+    """
     ``asdict`` only works on attrs instances, this works on anything.
     """
     if getattr(val.__class__, "__attrs_attrs__", None) is not None:
@@ -172,40 +172,40 @@ def astuple(
     retain_collection_types=False,
 ):
     """
-    Return the ``attrs`` attribute values of *inst* as a tuple. 
- 
-    Optionally recurse into other ``attrs``-decorated classes. 
- 
-    :param inst: Instance of an ``attrs``-decorated class. 
-    :param bool recurse: Recurse into classes that are also 
-        ``attrs``-decorated. 
-    :param callable filter: A callable whose return code determines whether an 
-        attribute or element is included (``True``) or dropped (``False``).  Is 
+    Return the ``attrs`` attribute values of *inst* as a tuple.
+
+    Optionally recurse into other ``attrs``-decorated classes.
+
+    :param inst: Instance of an ``attrs``-decorated class.
+    :param bool recurse: Recurse into classes that are also
+        ``attrs``-decorated.
+    :param callable filter: A callable whose return code determines whether an
+        attribute or element is included (``True``) or dropped (``False``).  Is
         called with the `attr.Attribute` as the first argument and the
-        value as the second argument. 
-    :param callable tuple_factory: A callable to produce tuples from.  For 
-        example, to produce lists instead of tuples. 
-    :param bool retain_collection_types: Do not convert to ``list`` 
-        or ``dict`` when encountering an attribute which type is 
-        ``tuple``, ``dict`` or ``set``.  Only meaningful if ``recurse`` is 
-        ``True``. 
- 
-    :rtype: return type of *tuple_factory* 
- 
-    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs`` 
-        class. 
- 
-    ..  versionadded:: 16.2.0 
-    """ 
-    attrs = fields(inst.__class__) 
-    rv = [] 
-    retain = retain_collection_types  # Very long. :/ 
-    for a in attrs: 
-        v = getattr(inst, a.name) 
-        if filter is not None and not filter(a, v): 
-            continue 
-        if recurse is True: 
-            if has(v.__class__): 
+        value as the second argument.
+    :param callable tuple_factory: A callable to produce tuples from.  For
+        example, to produce lists instead of tuples.
+    :param bool retain_collection_types: Do not convert to ``list``
+        or ``dict`` when encountering an attribute which type is
+        ``tuple``, ``dict`` or ``set``.  Only meaningful if ``recurse`` is
+        ``True``.
+
+    :rtype: return type of *tuple_factory*
+
+    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
+        class.
+
+    ..  versionadded:: 16.2.0
+    """
+    attrs = fields(inst.__class__)
+    rv = []
+    retain = retain_collection_types  # Very long. :/
+    for a in attrs:
+        v = getattr(inst, a.name)
+        if filter is not None and not filter(a, v):
+            continue
+        if recurse is True:
+            if has(v.__class__):
                 rv.append(
                     astuple(
                         v,
@@ -216,7 +216,7 @@ def astuple(
                     )
                 )
             elif isinstance(v, (tuple, list, set, frozenset)):
-                cf = v.__class__ if retain is True else list 
+                cf = v.__class__ if retain is True else list
                 rv.append(
                     cf(
                         [
@@ -233,114 +233,114 @@ def astuple(
                         ]
                     )
                 )
-            elif isinstance(v, dict): 
-                df = v.__class__ if retain is True else dict 
+            elif isinstance(v, dict):
+                df = v.__class__ if retain is True else dict
                 rv.append(
                     df(
-                        ( 
-                            astuple( 
-                                kk, 
-                                tuple_factory=tuple_factory, 
+                        (
+                            astuple(
+                                kk,
+                                tuple_factory=tuple_factory,
                                 retain_collection_types=retain,
                             )
                             if has(kk.__class__)
                             else kk,
-                            astuple( 
-                                vv, 
-                                tuple_factory=tuple_factory, 
+                            astuple(
+                                vv,
+                                tuple_factory=tuple_factory,
                                 retain_collection_types=retain,
                             )
                             if has(vv.__class__)
                             else vv,
-                        ) 
+                        )
                         for kk, vv in iteritems(v)
                     )
                 )
-            else: 
-                rv.append(v) 
-        else: 
-            rv.append(v) 
-
-    return rv if tuple_factory is list else tuple_factory(rv) 
- 
- 
-def has(cls): 
-    """ 
-    Check whether *cls* is a class with ``attrs`` attributes. 
- 
-    :param type cls: Class to introspect. 
-    :raise TypeError: If *cls* is not a class. 
- 
+            else:
+                rv.append(v)
+        else:
+            rv.append(v)
+
+    return rv if tuple_factory is list else tuple_factory(rv)
+
+
+def has(cls):
+    """
+    Check whether *cls* is a class with ``attrs`` attributes.
+
+    :param type cls: Class to introspect.
+    :raise TypeError: If *cls* is not a class.
+
     :rtype: bool
-    """ 
-    return getattr(cls, "__attrs_attrs__", None) is not None 
- 
- 
-def assoc(inst, **changes): 
-    """ 
-    Copy *inst* and apply *changes*. 
- 
-    :param inst: Instance of a class with ``attrs`` attributes. 
-    :param changes: Keyword changes in the new copy. 
- 
-    :return: A copy of inst with *changes* incorporated. 
- 
-    :raise attr.exceptions.AttrsAttributeNotFoundError: If *attr_name* couldn't 
-        be found on *cls*. 
-    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs`` 
-        class. 
- 
-    ..  deprecated:: 17.1.0 
+    """
+    return getattr(cls, "__attrs_attrs__", None) is not None
+
+
+def assoc(inst, **changes):
+    """
+    Copy *inst* and apply *changes*.
+
+    :param inst: Instance of a class with ``attrs`` attributes.
+    :param changes: Keyword changes in the new copy.
+
+    :return: A copy of inst with *changes* incorporated.
+
+    :raise attr.exceptions.AttrsAttributeNotFoundError: If *attr_name* couldn't
+        be found on *cls*.
+    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
+        class.
+
+    ..  deprecated:: 17.1.0
         Use `evolve` instead.
-    """ 
-    import warnings 
+    """
+    import warnings
 
     warnings.warn(
         "assoc is deprecated and will be removed after 2018/01.",
         DeprecationWarning,
         stacklevel=2,
     )
-    new = copy.copy(inst) 
-    attrs = fields(inst.__class__) 
-    for k, v in iteritems(changes): 
-        a = getattr(attrs, k, NOTHING) 
-        if a is NOTHING: 
-            raise AttrsAttributeNotFoundError( 
+    new = copy.copy(inst)
+    attrs = fields(inst.__class__)
+    for k, v in iteritems(changes):
+        a = getattr(attrs, k, NOTHING)
+        if a is NOTHING:
+            raise AttrsAttributeNotFoundError(
                 "{k} is not an attrs attribute on {cl}.".format(
                     k=k, cl=new.__class__
                 )
-            ) 
-        _obj_setattr(new, k, v) 
-    return new 
- 
- 
-def evolve(inst, **changes): 
-    """ 
-    Create a new instance, based on *inst* with *changes* applied. 
- 
-    :param inst: Instance of a class with ``attrs`` attributes. 
-    :param changes: Keyword changes in the new copy. 
- 
-    :return: A copy of inst with *changes* incorporated. 
- 
-    :raise TypeError: If *attr_name* couldn't be found in the class 
-        ``__init__``. 
-    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs`` 
-        class. 
- 
-    ..  versionadded:: 17.1.0 
-    """ 
-    cls = inst.__class__ 
-    attrs = fields(cls) 
-    for a in attrs: 
-        if not a.init: 
-            continue 
-        attr_name = a.name  # To deal with private attributes. 
-        init_name = attr_name if attr_name[0] != "_" else attr_name[1:] 
-        if init_name not in changes: 
-            changes[init_name] = getattr(inst, attr_name) 
-
-    return cls(**changes) 
+            )
+        _obj_setattr(new, k, v)
+    return new
+
+
+def evolve(inst, **changes):
+    """
+    Create a new instance, based on *inst* with *changes* applied.
+
+    :param inst: Instance of a class with ``attrs`` attributes.
+    :param changes: Keyword changes in the new copy.
+
+    :return: A copy of inst with *changes* incorporated.
+
+    :raise TypeError: If *attr_name* couldn't be found in the class
+        ``__init__``.
+    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
+        class.
+
+    ..  versionadded:: 17.1.0
+    """
+    cls = inst.__class__
+    attrs = fields(cls)
+    for a in attrs:
+        if not a.init:
+            continue
+        attr_name = a.name  # To deal with private attributes.
+        init_name = attr_name if attr_name[0] != "_" else attr_name[1:]
+        if init_name not in changes:
+            changes[init_name] = getattr(inst, attr_name)
+
+    return cls(**changes)
 
 
 def resolve_types(cls, globalns=None, localns=None, attribs=None):
diff --git a/contrib/python/attrs/attr/_make.py b/contrib/python/attrs/attr/_make.py
index e5d9352970..a1912b1233 100644
--- a/contrib/python/attrs/attr/_make.py
+++ b/contrib/python/attrs/attr/_make.py
@@ -1,17 +1,17 @@
-from __future__ import absolute_import, division, print_function 
- 
+from __future__ import absolute_import, division, print_function
+
 import copy
 import inspect
-import linecache 
-import sys 
-import threading 
+import linecache
+import sys
+import threading
 import uuid
-import warnings 
- 
-from operator import itemgetter 
- 
+import warnings
+
+from operator import itemgetter
+
 from . import _config, setters
-from ._compat import ( 
+from ._compat import (
     PY2,
     PYPY,
     isclass,
@@ -20,24 +20,24 @@ from ._compat import (
     new_class,
     ordered_dict,
     set_closure_cell,
-) 
-from .exceptions import ( 
+)
+from .exceptions import (
     DefaultAlreadySetError,
     FrozenInstanceError,
     NotAnAttrsClassError,
     PythonTooOldError,
     UnannotatedAttributeError,
-) 
- 
- 
+)
+
+
 if not PY2:
     import typing
 
 
-# This is used at least twice, so cache it here. 
-_obj_setattr = object.__setattr__ 
+# This is used at least twice, so cache it here.
+_obj_setattr = object.__setattr__
 _init_converter_pat = "__attr_converter_%s"
-_init_factory_pat = "__attr_factory_{}" 
+_init_factory_pat = "__attr_factory_{}"
 _tuple_property_pat = (
     "    {attr_name} = _attrs_property(_attrs_itemgetter({index}))"
 )
@@ -51,45 +51,45 @@ _classvar_prefixes = (
 # name mangling when trying to create a slot for the field
 # (when slots=True)
 _hash_cache_field = "_attrs_cached_hash"
- 
-_empty_metadata_singleton = metadata_proxy({}) 
- 
+
+_empty_metadata_singleton = metadata_proxy({})
+
 # Unique object for unequivocal getattr() defaults.
 _sentinel = object()
- 
 
-class _Nothing(object): 
-    """ 
-    Sentinel class to indicate the lack of a value when ``None`` is ambiguous. 
- 
+
+class _Nothing(object):
+    """
+    Sentinel class to indicate the lack of a value when ``None`` is ambiguous.
+
     ``_Nothing`` is a singleton. There is only ever one of it.
 
     .. versionchanged:: 21.1.0 ``bool(NOTHING)`` is now False.
-    """ 
- 
+    """
+
     _singleton = None
- 
+
     def __new__(cls):
         if _Nothing._singleton is None:
             _Nothing._singleton = super(_Nothing, cls).__new__(cls)
         return _Nothing._singleton
- 
-    def __repr__(self): 
-        return "NOTHING" 
- 
+
+    def __repr__(self):
+        return "NOTHING"
+
     def __bool__(self):
         return False
- 
+
     def __len__(self):
         return 0  # __bool__ for Python 2
 
 
-NOTHING = _Nothing() 
-""" 
-Sentinel to indicate the lack of a value when ``None`` is ambiguous. 
-""" 
- 
- 
+NOTHING = _Nothing()
+"""
+Sentinel to indicate the lack of a value when ``None`` is ambiguous.
+"""
+
+
 class _CacheHashWrapper(int):
     """
     An integer subclass that pickles / copies as None
@@ -131,51 +131,51 @@ def attrib(
     order=None,
     on_setattr=None,
 ):
-    """ 
-    Create a new attribute on a class. 
- 
-    ..  warning:: 
- 
-        Does *not* do anything unless the class is also decorated with 
+    """
+    Create a new attribute on a class.
+
+    ..  warning::
+
+        Does *not* do anything unless the class is also decorated with
         `attr.s`!
- 
-    :param default: A value that is used if an ``attrs``-generated ``__init__`` 
-        is used and no value is passed while instantiating or the attribute is 
-        excluded using ``init=False``. 
- 
+
+    :param default: A value that is used if an ``attrs``-generated ``__init__``
+        is used and no value is passed while instantiating or the attribute is
+        excluded using ``init=False``.
+
         If the value is an instance of `Factory`, its callable will be
-        used to construct a new value (useful for mutable data types like lists 
-        or dicts). 
- 
+        used to construct a new value (useful for mutable data types like lists
+        or dicts).
+
         If a default is not set (or set manually to `attr.NOTHING`), a value
         *must* be supplied when instantiating; otherwise a `TypeError`
-        will be raised. 
- 
-        The default can also be set using decorator notation as shown below. 
- 
+        will be raised.
+
+        The default can also be set using decorator notation as shown below.
+
     :type default: Any value
- 
-    :param callable factory: Syntactic sugar for 
+
+    :param callable factory: Syntactic sugar for
         ``default=attr.Factory(factory)``.
- 
+
     :param validator: `callable` that is called by ``attrs``-generated
-        ``__init__`` methods after the instance has been initialized.  They 
+        ``__init__`` methods after the instance has been initialized.  They
         receive the initialized instance, the `Attribute`, and the
-        passed value. 
- 
-        The return value is *not* inspected so the validator has to throw an 
-        exception itself. 
- 
+        passed value.
+
+        The return value is *not* inspected so the validator has to throw an
+        exception itself.
+
         If a `list` is passed, its items are treated as validators and must
-        all pass. 
- 
-        Validators can be globally disabled and re-enabled using 
+        all pass.
+
+        Validators can be globally disabled and re-enabled using
         `get_run_validators`.
- 
-        The validator can also be set using decorator notation as shown below. 
- 
+
+        The validator can also be set using decorator notation as shown below.
+
     :type validator: `callable` or a `list` of `callable`\\ s.
- 
+
     :param repr: Include this attribute in the generated ``__repr__``
         method. If ``True``, include the attribute; if ``False``, omit it. By
         default, the built-in ``repr()`` function is used. To override how the
@@ -207,24 +207,24 @@ def attrib(
         ``__hash__`` method.  If ``None`` (default), mirror *eq*'s value.  This
         is the correct behavior according the Python spec.  Setting this value
         to anything else than ``None`` is *discouraged*.
-    :param bool init: Include this attribute in the generated ``__init__`` 
-        method.  It is possible to set this to ``False`` and set a default 
-        value.  In that case this attributed is unconditionally initialized 
-        with the specified default value or factory. 
+    :param bool init: Include this attribute in the generated ``__init__``
+        method.  It is possible to set this to ``False`` and set a default
+        value.  In that case this attributed is unconditionally initialized
+        with the specified default value or factory.
     :param callable converter: `callable` that is called by
         ``attrs``-generated ``__init__`` methods to convert attribute's value
-        to the desired format.  It is given the passed-in value, and the 
-        returned value will be used as the new value of the attribute.  The 
-        value is converted before being passed to the validator, if any. 
-    :param metadata: An arbitrary mapping, to be used by third-party 
+        to the desired format.  It is given the passed-in value, and the
+        returned value will be used as the new value of the attribute.  The
+        value is converted before being passed to the validator, if any.
+    :param metadata: An arbitrary mapping, to be used by third-party
         components.  See `extending_metadata`.
-    :param type: The type of the attribute.  In Python 3.6 or greater, the 
-        preferred method to specify the type is using a variable annotation 
-        (see `PEP 526 <https://www.python.org/dev/peps/pep-0526/>`_). 
-        This argument is provided for backward compatibility. 
-        Regardless of the approach used, the type will be stored on 
-        ``Attribute.type``. 
- 
+    :param type: The type of the attribute.  In Python 3.6 or greater, the
+        preferred method to specify the type is using a variable annotation
+        (see `PEP 526 <https://www.python.org/dev/peps/pep-0526/>`_).
+        This argument is provided for backward compatibility.
+        Regardless of the approach used, the type will be stored on
+        ``Attribute.type``.
+
         Please note that ``attrs`` doesn't do anything with this metadata by
         itself. You can use it as part of your own code or for
         `static type checking <types>`.
@@ -238,17 +238,17 @@ def attrib(
     :type on_setattr: `callable`, or a list of callables, or `None`, or
         `attr.setters.NO_OP`
 
-    .. versionadded:: 15.2.0 *convert* 
-    .. versionadded:: 16.3.0 *metadata* 
-    .. versionchanged:: 17.1.0 *validator* can be a ``list`` now. 
-    .. versionchanged:: 17.1.0 
+    .. versionadded:: 15.2.0 *convert*
+    .. versionadded:: 16.3.0 *metadata*
+    .. versionchanged:: 17.1.0 *validator* can be a ``list`` now.
+    .. versionchanged:: 17.1.0
        *hash* is ``None`` and therefore mirrors *eq* by default.
-    .. versionadded:: 17.3.0 *type* 
-    .. deprecated:: 17.4.0 *convert* 
-    .. versionadded:: 17.4.0 *converter* as a replacement for the deprecated 
-       *convert* to achieve consistency with other noun-based arguments. 
-    .. versionadded:: 18.1.0 
-       ``factory=f`` is syntactic sugar for ``default=attr.Factory(f)``. 
+    .. versionadded:: 17.3.0 *type*
+    .. deprecated:: 17.4.0 *convert*
+    .. versionadded:: 17.4.0 *converter* as a replacement for the deprecated
+       *convert* to achieve consistency with other noun-based arguments.
+    .. versionadded:: 18.1.0
+       ``factory=f`` is syntactic sugar for ``default=attr.Factory(f)``.
     .. versionadded:: 18.2.0 *kw_only*
     .. versionchanged:: 19.2.0 *convert* keyword argument removed.
     .. versionchanged:: 19.2.0 *repr* also accepts a custom callable.
@@ -259,29 +259,29 @@ def attrib(
     .. versionchanged:: 21.1.0
        *eq*, *order*, and *cmp* also accept a custom callable
     .. versionchanged:: 21.1.0 *cmp* undeprecated
-    """ 
+    """
     eq, eq_key, order, order_key = _determine_attrib_eq_order(
         cmp, eq, order, True
     )
 
-    if hash is not None and hash is not True and hash is not False: 
-        raise TypeError( 
-            "Invalid value for hash.  Must be True, False, or None." 
-        ) 
- 
-    if factory is not None: 
-        if default is not NOTHING: 
-            raise ValueError( 
-                "The `default` and `factory` arguments are mutually " 
-                "exclusive." 
-            ) 
-        if not callable(factory): 
+    if hash is not None and hash is not True and hash is not False:
+        raise TypeError(
+            "Invalid value for hash.  Must be True, False, or None."
+        )
+
+    if factory is not None:
+        if default is not NOTHING:
+            raise ValueError(
+                "The `default` and `factory` arguments are mutually "
+                "exclusive."
+            )
+        if not callable(factory):
             raise ValueError("The `factory` argument must be a callable.")
-        default = Factory(factory) 
- 
-    if metadata is None: 
-        metadata = {} 
- 
+        default = Factory(factory)
+
+    if metadata is None:
+        metadata = {}
+
     # Apply syntactic sugar by auto-wrapping.
     if isinstance(on_setattr, (list, tuple)):
         on_setattr = setters.pipe(*on_setattr)
@@ -292,25 +292,25 @@ def attrib(
     if converter and isinstance(converter, (list, tuple)):
         converter = pipe(*converter)
 
-    return _CountingAttr( 
-        default=default, 
-        validator=validator, 
-        repr=repr, 
+    return _CountingAttr(
+        default=default,
+        validator=validator,
+        repr=repr,
         cmp=None,
-        hash=hash, 
-        init=init, 
-        converter=converter, 
-        metadata=metadata, 
-        type=type, 
+        hash=hash,
+        init=init,
+        converter=converter,
+        metadata=metadata,
+        type=type,
         kw_only=kw_only,
         eq=eq,
         eq_key=eq_key,
         order=order,
         order_key=order_key,
         on_setattr=on_setattr,
-    ) 
- 
- 
+    )
+
+
 def _compile_and_eval(script, globs, locs=None, filename=""):
     """
     "Exec" the script with the given global (globs) and local (locs) variables.
@@ -341,34 +341,34 @@ def _make_method(name, script, filename, globs=None):
     return locs[name]
 
 
-def _make_attr_tuple_class(cls_name, attr_names): 
-    """ 
-    Create a tuple subclass to hold `Attribute`s for an `attrs` class. 
- 
-    The subclass is a bare tuple with properties for names. 
- 
-    class MyClassAttributes(tuple): 
-        __slots__ = () 
-        x = property(itemgetter(0)) 
-    """ 
-    attr_class_name = "{}Attributes".format(cls_name) 
-    attr_class_template = [ 
-        "class {}(tuple):".format(attr_class_name), 
-        "    __slots__ = ()", 
-    ] 
-    if attr_names: 
-        for i, attr_name in enumerate(attr_names): 
+def _make_attr_tuple_class(cls_name, attr_names):
+    """
+    Create a tuple subclass to hold `Attribute`s for an `attrs` class.
+
+    The subclass is a bare tuple with properties for names.
+
+    class MyClassAttributes(tuple):
+        __slots__ = ()
+        x = property(itemgetter(0))
+    """
+    attr_class_name = "{}Attributes".format(cls_name)
+    attr_class_template = [
+        "class {}(tuple):".format(attr_class_name),
+        "    __slots__ = ()",
+    ]
+    if attr_names:
+        for i, attr_name in enumerate(attr_names):
             attr_class_template.append(
                 _tuple_property_pat.format(index=i, attr_name=attr_name)
             )
-    else: 
-        attr_class_template.append("    pass") 
+    else:
+        attr_class_template.append("    pass")
     globs = {"_attrs_itemgetter": itemgetter, "_attrs_property": property}
     _compile_and_eval("\n".join(attr_class_template), globs)
-    return globs[attr_class_name] 
- 
- 
-# Tuple class for extracted attributes from a class definition. 
+    return globs[attr_class_name]
+
+
+# Tuple class for extracted attributes from a class definition.
 # `base_attrs` is a subset of `attrs`.
 _Attributes = _make_attr_tuple_class(
     "_Attributes",
@@ -381,22 +381,22 @@ _Attributes = _make_attr_tuple_class(
         "base_attrs_map",
     ],
 )
- 
- 
-def _is_class_var(annot): 
-    """ 
-    Check whether *annot* is a typing.ClassVar. 
- 
-    The string comparison hack is used to avoid evaluating all string 
-    annotations which would put attrs-based classes at a performance 
-    disadvantage compared to plain old classes. 
-    """ 
+
+
+def _is_class_var(annot):
+    """
+    Check whether *annot* is a typing.ClassVar.
+
+    The string comparison hack is used to avoid evaluating all string
+    annotations which would put attrs-based classes at a performance
+    disadvantage compared to plain old classes.
+    """
     annot = str(annot)
- 
+
     # Annotation can be quoted.
     if annot.startswith(("'", '"')) and annot.endswith(("'", '"')):
         annot = annot[1:-1]
- 
+
     return annot.startswith(_classvar_prefixes)
 
 
@@ -418,25 +418,25 @@ def _has_own_attribute(cls, attrib_name):
     return True
 
 
-def _get_annotations(cls): 
-    """ 
-    Get annotations for *cls*. 
-    """ 
+def _get_annotations(cls):
+    """
+    Get annotations for *cls*.
+    """
     if _has_own_attribute(cls, "__annotations__"):
         return cls.__annotations__
- 
+
     return {}
- 
- 
-def _counter_getter(e): 
-    """ 
-    Key function for sorting to avoid re-creating a lambda for every class. 
-    """ 
-    return e[1].counter 
- 
- 
+
+
+def _counter_getter(e):
+    """
+    Key function for sorting to avoid re-creating a lambda for every class.
+    """
+    return e[1].counter
+
+
 def _collect_base_attrs(cls, taken_attr_names):
-    """ 
+    """
     Collect attr.ibs from base classes of *cls*, except *taken_attr_names*.
     """
     base_attrs = []
@@ -498,54 +498,54 @@ def _transform_attrs(
     cls, these, auto_attribs, kw_only, collect_by_mro, field_transformer
 ):
     """
-    Transform all `_CountingAttr`s on a class into `Attribute`s. 
- 
-    If *these* is passed, use that and don't look for them on the class. 
- 
+    Transform all `_CountingAttr`s on a class into `Attribute`s.
+
+    If *these* is passed, use that and don't look for them on the class.
+
     *collect_by_mro* is True, collect them in the correct MRO order, otherwise
     use the old -- incorrect -- order.  See #428.
 
-    Return an `_Attributes`. 
-    """ 
-    cd = cls.__dict__ 
-    anns = _get_annotations(cls) 
- 
-    if these is not None: 
+    Return an `_Attributes`.
+    """
+    cd = cls.__dict__
+    anns = _get_annotations(cls)
+
+    if these is not None:
         ca_list = [(name, ca) for name, ca in iteritems(these)]
- 
-        if not isinstance(these, ordered_dict): 
-            ca_list.sort(key=_counter_getter) 
-    elif auto_attribs is True: 
-        ca_names = { 
-            name 
+
+        if not isinstance(these, ordered_dict):
+            ca_list.sort(key=_counter_getter)
+    elif auto_attribs is True:
+        ca_names = {
+            name
             for name, attr in cd.items()
-            if isinstance(attr, _CountingAttr) 
-        } 
-        ca_list = [] 
-        annot_names = set() 
-        for attr_name, type in anns.items(): 
-            if _is_class_var(type): 
-                continue 
-            annot_names.add(attr_name) 
-            a = cd.get(attr_name, NOTHING) 
-
-            if not isinstance(a, _CountingAttr): 
-                if a is NOTHING: 
-                    a = attrib() 
-                else: 
-                    a = attrib(default=a) 
-            ca_list.append((attr_name, a)) 
- 
-        unannotated = ca_names - annot_names 
-        if len(unannotated) > 0: 
-            raise UnannotatedAttributeError( 
+            if isinstance(attr, _CountingAttr)
+        }
+        ca_list = []
+        annot_names = set()
+        for attr_name, type in anns.items():
+            if _is_class_var(type):
+                continue
+            annot_names.add(attr_name)
+            a = cd.get(attr_name, NOTHING)
+
+            if not isinstance(a, _CountingAttr):
+                if a is NOTHING:
+                    a = attrib()
+                else:
+                    a = attrib(default=a)
+            ca_list.append((attr_name, a))
+
+        unannotated = ca_names - annot_names
+        if len(unannotated) > 0:
+            raise UnannotatedAttributeError(
                 "The following `attr.ib`s lack a type annotation: "
                 + ", ".join(
                     sorted(unannotated, key=lambda n: cd.get(n).counter)
                 )
                 + "."
-            ) 
-    else: 
+            )
+    else:
         ca_list = sorted(
             (
                 (name, attr)
@@ -554,14 +554,14 @@ def _transform_attrs(
             ),
             key=lambda e: e[1].counter,
         )
- 
-    own_attrs = [ 
-        Attribute.from_counting_attr( 
+
+    own_attrs = [
+        Attribute.from_counting_attr(
             name=attr_name, ca=ca, type=anns.get(attr_name)
-        ) 
+        )
         for attr_name, ca in ca_list
-    ] 
- 
+    ]
+
     if collect_by_mro:
         base_attrs, base_attr_map = _collect_base_attrs(
             cls, {a.name for a in own_attrs}
@@ -570,39 +570,39 @@ def _transform_attrs(
         base_attrs, base_attr_map = _collect_base_attrs_broken(
             cls, {a.name for a in own_attrs}
         )
- 
+
     attr_names = [a.name for a in base_attrs + own_attrs]
- 
-    AttrsClass = _make_attr_tuple_class(cls.__name__, attr_names) 
- 
+
+    AttrsClass = _make_attr_tuple_class(cls.__name__, attr_names)
+
     if kw_only:
         own_attrs = [a.evolve(kw_only=True) for a in own_attrs]
         base_attrs = [a.evolve(kw_only=True) for a in base_attrs]
- 
+
     attrs = AttrsClass(base_attrs + own_attrs)
 
     # Mandatory vs non-mandatory attr order only matters when they are part of
     # the __init__ signature and when they aren't kw_only (which are moved to
     # the end and can be mandatory or non-mandatory in any order, as they will
     # be specified as keyword args anyway). Check the order of those attrs:
-    had_default = False 
+    had_default = False
     for a in (a for a in attrs if a.init is not False and a.kw_only is False):
         if had_default is True and a.default is NOTHING:
-            raise ValueError( 
-                "No mandatory attributes allowed after an attribute with a " 
+            raise ValueError(
+                "No mandatory attributes allowed after an attribute with a "
                 "default value or factory.  Attribute in question: %r" % (a,)
-            ) 
+            )
 
         if had_default is False and a.default is not NOTHING:
-            had_default = True 
- 
+            had_default = True
+
     if field_transformer is not None:
         attrs = field_transformer(cls, attrs)
     return _Attributes((attrs, base_attrs, base_attr_map))
- 
- 
+
+
 if PYPY:
- 
+
     def _frozen_setattrs(self, name, value):
         """
         Attached to frozen classes as __setattr__.
@@ -613,7 +613,7 @@ if PYPY:
         ):
             BaseException.__setattr__(self, name, value)
             return
- 
+
         raise FrozenInstanceError()
 
 
@@ -626,19 +626,19 @@ else:
         raise FrozenInstanceError()
 
 
-def _frozen_delattrs(self, name): 
-    """ 
-    Attached to frozen classes as __delattr__. 
-    """ 
-    raise FrozenInstanceError() 
- 
- 
-class _ClassBuilder(object): 
-    """ 
-    Iteratively build *one* class. 
-    """ 
+def _frozen_delattrs(self, name):
+    """
+    Attached to frozen classes as __delattr__.
+    """
+    raise FrozenInstanceError()
+
 
-    __slots__ = ( 
+class _ClassBuilder(object):
+    """
+    Iteratively build *one* class.
+    """
+
+    __slots__ = (
         "_attr_names",
         "_attrs",
         "_base_attr_map",
@@ -656,8 +656,8 @@ class _ClassBuilder(object):
         "_weakref_slot",
         "_has_own_setattr",
         "_has_custom_setattr",
-    ) 
- 
+    )
+
     def __init__(
         self,
         cls,
@@ -682,33 +682,33 @@ class _ClassBuilder(object):
             kw_only,
             collect_by_mro,
             field_transformer,
-        ) 
- 
-        self._cls = cls 
-        self._cls_dict = dict(cls.__dict__) if slots else {} 
-        self._attrs = attrs 
+        )
+
+        self._cls = cls
+        self._cls_dict = dict(cls.__dict__) if slots else {}
+        self._attrs = attrs
         self._base_names = set(a.name for a in base_attrs)
         self._base_attr_map = base_map
-        self._attr_names = tuple(a.name for a in attrs) 
-        self._slots = slots 
+        self._attr_names = tuple(a.name for a in attrs)
+        self._slots = slots
         self._frozen = frozen
         self._weakref_slot = weakref_slot
         self._cache_hash = cache_hash
         self._has_pre_init = bool(getattr(cls, "__attrs_pre_init__", False))
-        self._has_post_init = bool(getattr(cls, "__attrs_post_init__", False)) 
-        self._delete_attribs = not bool(these) 
+        self._has_post_init = bool(getattr(cls, "__attrs_post_init__", False))
+        self._delete_attribs = not bool(these)
         self._is_exc = is_exc
         self._on_setattr = on_setattr
- 
+
         self._has_custom_setattr = has_custom_setattr
         self._has_own_setattr = False
 
-        self._cls_dict["__attrs_attrs__"] = self._attrs 
- 
-        if frozen: 
-            self._cls_dict["__setattr__"] = _frozen_setattrs 
-            self._cls_dict["__delattr__"] = _frozen_delattrs 
- 
+        self._cls_dict["__attrs_attrs__"] = self._attrs
+
+        if frozen:
+            self._cls_dict["__setattr__"] = _frozen_setattrs
+            self._cls_dict["__delattr__"] = _frozen_delattrs
+
             self._has_own_setattr = True
 
         if getstate_setstate:
@@ -717,30 +717,30 @@ class _ClassBuilder(object):
                 self._cls_dict["__setstate__"],
             ) = self._make_getstate_setstate()
 
-    def __repr__(self): 
-        return "<_ClassBuilder(cls={cls})>".format(cls=self._cls.__name__) 
- 
-    def build_class(self): 
-        """ 
-        Finalize class based on the accumulated configuration. 
- 
+    def __repr__(self):
+        return "<_ClassBuilder(cls={cls})>".format(cls=self._cls.__name__)
+
+    def build_class(self):
+        """
+        Finalize class based on the accumulated configuration.
+
         Builder cannot be used after calling this method.
-        """ 
-        if self._slots is True: 
-            return self._create_slots_class() 
-        else: 
-            return self._patch_original_class() 
- 
-    def _patch_original_class(self): 
-        """ 
-        Apply accumulated methods and return the class. 
-        """ 
-        cls = self._cls 
+        """
+        if self._slots is True:
+            return self._create_slots_class()
+        else:
+            return self._patch_original_class()
+
+    def _patch_original_class(self):
+        """
+        Apply accumulated methods and return the class.
+        """
+        cls = self._cls
         base_names = self._base_names
- 
-        # Clean class of attribute definitions (`attr.ib()`s). 
-        if self._delete_attribs: 
-            for name in self._attr_names: 
+
+        # Clean class of attribute definitions (`attr.ib()`s).
+        if self._delete_attribs:
+            for name in self._attr_names:
                 if (
                     name not in base_names
                     and getattr(cls, name, _sentinel) is not _sentinel
@@ -752,11 +752,11 @@ class _ClassBuilder(object):
                         # variable and we want to set an attribute with the
                         # same name by using only a type annotation.
                         pass
- 
-        # Attach our dunder methods. 
-        for name, value in self._cls_dict.items(): 
-            setattr(cls, name, value) 
- 
+
+        # Attach our dunder methods.
+        for name, value in self._cls_dict.items():
+            setattr(cls, name, value)
+
         # If we've inherited an attrs __setattr__ and don't write our own,
         # reset it to object's.
         if not self._has_own_setattr and getattr(
@@ -767,18 +767,18 @@ class _ClassBuilder(object):
             if not self._has_custom_setattr:
                 cls.__setattr__ = object.__setattr__
 
-        return cls 
- 
-    def _create_slots_class(self): 
-        """ 
-        Build and return a new class with a `__slots__` attribute. 
-        """ 
-        cd = { 
-            k: v 
-            for k, v in iteritems(self._cls_dict) 
+        return cls
+
+    def _create_slots_class(self):
+        """
+        Build and return a new class with a `__slots__` attribute.
+        """
+        cd = {
+            k: v
+            for k, v in iteritems(self._cls_dict)
             if k not in tuple(self._attr_names) + ("__dict__", "__weakref__")
-        } 
- 
+        }
+
         # If our class doesn't have its own implementation of __setattr__
         # (either from the user or by us), check the bases, if one of them has
         # an attrs-made __setattr__, that needs to be reset. We don't walk the
@@ -821,7 +821,7 @@ class _ClassBuilder(object):
         ):
             names += ("__weakref__",)
 
-        # We only add the names of attributes that aren't inherited. 
+        # We only add the names of attributes that aren't inherited.
         # Setting __slots__ to inherited attributes wastes memory.
         slot_names = [name for name in names if name not in base_names]
         # There are slots for attributes from current class
@@ -838,35 +838,35 @@ class _ClassBuilder(object):
         if self._cache_hash:
             slot_names.append(_hash_cache_field)
         cd["__slots__"] = tuple(slot_names)
- 
-        qualname = getattr(self._cls, "__qualname__", None) 
-        if qualname is not None: 
-            cd["__qualname__"] = qualname 
- 
-        # Create new class based on old class and our methods. 
+
+        qualname = getattr(self._cls, "__qualname__", None)
+        if qualname is not None:
+            cd["__qualname__"] = qualname
+
+        # Create new class based on old class and our methods.
         cls = type(self._cls)(self._cls.__name__, self._cls.__bases__, cd)
- 
-        # The following is a fix for 
-        # https://github.com/python-attrs/attrs/issues/102.  On Python 3, 
-        # if a method mentions `__class__` or uses the no-arg super(), the 
-        # compiler will bake a reference to the class in the method itself 
-        # as `method.__closure__`.  Since we replace the class with a 
-        # clone, we rewrite these references so it keeps working. 
-        for item in cls.__dict__.values(): 
-            if isinstance(item, (classmethod, staticmethod)): 
-                # Class- and staticmethods hide their functions inside. 
-                # These might need to be rewritten as well. 
-                closure_cells = getattr(item.__func__, "__closure__", None) 
+
+        # The following is a fix for
+        # https://github.com/python-attrs/attrs/issues/102.  On Python 3,
+        # if a method mentions `__class__` or uses the no-arg super(), the
+        # compiler will bake a reference to the class in the method itself
+        # as `method.__closure__`.  Since we replace the class with a
+        # clone, we rewrite these references so it keeps working.
+        for item in cls.__dict__.values():
+            if isinstance(item, (classmethod, staticmethod)):
+                # Class- and staticmethods hide their functions inside.
+                # These might need to be rewritten as well.
+                closure_cells = getattr(item.__func__, "__closure__", None)
             elif isinstance(item, property):
                 # Workaround for property `super()` shortcut (PY3-only).
                 # There is no universal way for other descriptors.
                 closure_cells = getattr(item.fget, "__closure__", None)
-            else: 
-                closure_cells = getattr(item, "__closure__", None) 
- 
-            if not closure_cells:  # Catch None or the empty list. 
-                continue 
-            for cell in closure_cells: 
+            else:
+                closure_cells = getattr(item, "__closure__", None)
+
+            if not closure_cells:  # Catch None or the empty list.
+                continue
+            for cell in closure_cells:
                 try:
                     match = cell.cell_contents is self._cls
                 except ValueError:  # ValueError: Cell is empty
@@ -874,28 +874,28 @@ class _ClassBuilder(object):
                 else:
                     if match:
                         set_closure_cell(cell, cls)
- 
-        return cls 
- 
-    def add_repr(self, ns): 
-        self._cls_dict["__repr__"] = self._add_method_dunders( 
-            _make_repr(self._attrs, ns=ns) 
-        ) 
-        return self 
- 
-    def add_str(self): 
-        repr = self._cls_dict.get("__repr__") 
-        if repr is None: 
-            raise ValueError( 
-                "__str__ can only be generated if a __repr__ exists." 
-            ) 
- 
-        def __str__(self): 
-            return self.__repr__() 
- 
-        self._cls_dict["__str__"] = self._add_method_dunders(__str__) 
-        return self 
- 
+
+        return cls
+
+    def add_repr(self, ns):
+        self._cls_dict["__repr__"] = self._add_method_dunders(
+            _make_repr(self._attrs, ns=ns)
+        )
+        return self
+
+    def add_str(self):
+        repr = self._cls_dict.get("__repr__")
+        if repr is None:
+            raise ValueError(
+                "__str__ can only be generated if a __repr__ exists."
+            )
+
+        def __str__(self):
+            return self.__repr__()
+
+        self._cls_dict["__str__"] = self._add_method_dunders(__str__)
+        return self
+
     def _make_getstate_setstate(self):
         """
         Create custom __setstate__ and __getstate__ methods.
@@ -930,42 +930,42 @@ class _ClassBuilder(object):
 
         return slots_getstate, slots_setstate
 
-    def make_unhashable(self): 
-        self._cls_dict["__hash__"] = None 
-        return self 
- 
-    def add_hash(self): 
-        self._cls_dict["__hash__"] = self._add_method_dunders( 
+    def make_unhashable(self):
+        self._cls_dict["__hash__"] = None
+        return self
+
+    def add_hash(self):
+        self._cls_dict["__hash__"] = self._add_method_dunders(
             _make_hash(
                 self._cls,
                 self._attrs,
                 frozen=self._frozen,
                 cache_hash=self._cache_hash,
             )
-        ) 
- 
-        return self 
- 
-    def add_init(self): 
-        self._cls_dict["__init__"] = self._add_method_dunders( 
-            _make_init( 
+        )
+
+        return self
+
+    def add_init(self):
+        self._cls_dict["__init__"] = self._add_method_dunders(
+            _make_init(
                 self._cls,
-                self._attrs, 
+                self._attrs,
                 self._has_pre_init,
-                self._has_post_init, 
-                self._frozen, 
-                self._slots, 
+                self._has_post_init,
+                self._frozen,
+                self._slots,
                 self._cache_hash,
                 self._base_attr_map,
                 self._is_exc,
                 self._on_setattr is not None
                 and self._on_setattr is not setters.NO_OP,
                 attrs_init=False,
-            ) 
-        ) 
- 
-        return self 
- 
+            )
+        )
+
+        return self
+
     def add_attrs_init(self):
         self._cls_dict["__attrs_init__"] = self._add_method_dunders(
             _make_init(
@@ -987,15 +987,15 @@ class _ClassBuilder(object):
         return self
 
     def add_eq(self):
-        cd = self._cls_dict 
- 
+        cd = self._cls_dict
+
         cd["__eq__"] = self._add_method_dunders(
             _make_eq(self._cls, self._attrs)
         )
         cd["__ne__"] = self._add_method_dunders(_make_ne())
- 
-        return self 
- 
+
+        return self
+
     def add_order(self):
         cd = self._cls_dict
 
@@ -1042,22 +1042,22 @@ class _ClassBuilder(object):
 
         return self
 
-    def _add_method_dunders(self, method): 
-        """ 
-        Add __module__ and __qualname__ to a *method* if possible. 
-        """ 
-        try: 
-            method.__module__ = self._cls.__module__ 
-        except AttributeError: 
-            pass 
- 
-        try: 
-            method.__qualname__ = ".".join( 
+    def _add_method_dunders(self, method):
+        """
+        Add __module__ and __qualname__ to a *method* if possible.
+        """
+        try:
+            method.__module__ = self._cls.__module__
+        except AttributeError:
+            pass
+
+        try:
+            method.__qualname__ = ".".join(
                 (self._cls.__qualname__, method.__name__)
-            ) 
-        except AttributeError: 
-            pass 
- 
+            )
+        except AttributeError:
+            pass
+
         try:
             method.__doc__ = "Method generated by attrs for class %s." % (
                 self._cls.__qualname__,
@@ -1065,9 +1065,9 @@ class _ClassBuilder(object):
         except AttributeError:
             pass
 
-        return method 
- 
- 
+        return method
+
+
 _CMP_DEPRECATION = (
     "The usage of `cmp` is deprecated and will be removed on or after "
     "2021-06-01.  Please use `eq` and `order` instead."
@@ -1193,29 +1193,29 @@ def attrs(
     on_setattr=None,
     field_transformer=None,
 ):
-    r""" 
-    A class decorator that adds `dunder 
-    <https://wiki.python.org/moin/DunderAlias>`_\ -methods according to the 
+    r"""
+    A class decorator that adds `dunder
+    <https://wiki.python.org/moin/DunderAlias>`_\ -methods according to the
     specified attributes using `attr.ib` or the *these* argument.
- 
+
     :param these: A dictionary of name to `attr.ib` mappings.  This is
-        useful to avoid the definition of your attributes within the class body 
-        because you can't (e.g. if you want to add ``__repr__`` methods to 
-        Django models) or don't want to. 
- 
-        If *these* is not ``None``, ``attrs`` will *not* search the class body 
-        for attributes and will *not* remove any attributes from it. 
- 
+        useful to avoid the definition of your attributes within the class body
+        because you can't (e.g. if you want to add ``__repr__`` methods to
+        Django models) or don't want to.
+
+        If *these* is not ``None``, ``attrs`` will *not* search the class body
+        for attributes and will *not* remove any attributes from it.
+
         If *these* is an ordered dict (`dict` on Python 3.6+,
         `collections.OrderedDict` otherwise), the order is deduced from
-        the order of the attributes inside *these*.  Otherwise the order 
-        of the definition of the attributes is used. 
- 
+        the order of the attributes inside *these*.  Otherwise the order
+        of the definition of the attributes is used.
+
     :type these: `dict` of `str` to `attr.ib`
- 
-    :param str repr_ns: When using nested classes, there's no way in Python 2 
-        to automatically detect that.  Therefore it's possible to set the 
-        namespace explicitly for a more meaningful ``repr`` output. 
+
+    :param str repr_ns: When using nested classes, there's no way in Python 2
+        to automatically detect that.  Therefore it's possible to set the
+        namespace explicitly for a more meaningful ``repr`` output.
     :param bool auto_detect: Instead of setting the *init*, *repr*, *eq*,
         *order*, and *hash* arguments explicitly, assume they are set to
         ``True`` **unless any** of the involved methods for one of the
@@ -1242,10 +1242,10 @@ def attrs(
         *auto_detect* requires Python 3. Setting it ``True`` on Python 2 raises
         a `PythonTooOldError`.
 
-    :param bool repr: Create a ``__repr__`` method with a human readable 
-        representation of ``attrs`` attributes.. 
-    :param bool str: Create a ``__str__`` method that is identical to 
-        ``__repr__``.  This is usually not necessary except for 
+    :param bool repr: Create a ``__repr__`` method with a human readable
+        representation of ``attrs`` attributes..
+    :param bool str: Create a ``__str__`` method that is identical to
+        ``__repr__``.  This is usually not necessary except for
         `Exception`\ s.
     :param Optional[bool] eq: If ``True`` or ``None`` (default), add ``__eq__``
         and ``__ne__`` methods that check two instances for equality.
@@ -1260,24 +1260,24 @@ def attrs(
         and *order* to the same value. Must not be mixed with *eq* or *order*.
     :param Optional[bool] hash: If ``None`` (default), the ``__hash__`` method
         is generated according how *eq* and *frozen* are set.
- 
-        1. If *both* are True, ``attrs`` will generate a ``__hash__`` for you. 
+
+        1. If *both* are True, ``attrs`` will generate a ``__hash__`` for you.
         2. If *eq* is True and *frozen* is False, ``__hash__`` will be set to
-           None, marking it unhashable (which it is). 
+           None, marking it unhashable (which it is).
         3. If *eq* is False, ``__hash__`` will be left untouched meaning the
            ``__hash__`` method of the base class will be used (if base class is
-           ``object``, this means it will fall back to id-based hashing.). 
- 
-        Although not recommended, you can decide for yourself and force 
-        ``attrs`` to create one (e.g. if the class is immutable even though you 
-        didn't freeze it programmatically) by passing ``True`` or not.  Both of 
-        these cases are rather special and should be used carefully. 
- 
+           ``object``, this means it will fall back to id-based hashing.).
+
+        Although not recommended, you can decide for yourself and force
+        ``attrs`` to create one (e.g. if the class is immutable even though you
+        didn't freeze it programmatically) by passing ``True`` or not.  Both of
+        these cases are rather special and should be used carefully.
+
         See our documentation on `hashing`, Python's documentation on
         `object.__hash__`, and the `GitHub issue that led to the default \
         behavior <https://github.com/python-attrs/attrs/issues/136>`_ for more
         details.
-    :param bool init: Create a ``__init__`` method that initializes the 
+    :param bool init: Create a ``__init__`` method that initializes the
         ``attrs`` attributes. Leading underscores are stripped for the argument
         name. If a ``__attrs_pre_init__`` method exists on the class, it will
         be called before the class is initialized. If a ``__attrs_post_init__``
@@ -1292,47 +1292,47 @@ def attrs(
         memory-efficient. Slotted classes are generally superior to the default
         dict classes, but have some gotchas you should know about, so we
         encourage you to read the `glossary entry <slotted classes>`.
-    :param bool frozen: Make instances immutable after initialization.  If 
-        someone attempts to modify a frozen instance, 
+    :param bool frozen: Make instances immutable after initialization.  If
+        someone attempts to modify a frozen instance,
         `attr.exceptions.FrozenInstanceError` is raised.
- 
+
         .. note::
- 
-            1. This is achieved by installing a custom ``__setattr__`` method 
+
+            1. This is achieved by installing a custom ``__setattr__`` method
                on your class, so you can't implement your own.
- 
-            2. True immutability is impossible in Python. 
- 
+
+            2. True immutability is impossible in Python.
+
             3. This *does* have a minor a runtime performance `impact
-               <how-frozen>` when initializing new instances.  In other words: 
-               ``__init__`` is slightly slower with ``frozen=True``. 
- 
-            4. If a class is frozen, you cannot modify ``self`` in 
-               ``__attrs_post_init__`` or a self-written ``__init__``. You can 
-               circumvent that limitation by using 
-               ``object.__setattr__(self, "attribute_name", value)``. 
- 
+               <how-frozen>` when initializing new instances.  In other words:
+               ``__init__`` is slightly slower with ``frozen=True``.
+
+            4. If a class is frozen, you cannot modify ``self`` in
+               ``__attrs_post_init__`` or a self-written ``__init__``. You can
+               circumvent that limitation by using
+               ``object.__setattr__(self, "attribute_name", value)``.
+
             5. Subclasses of a frozen class are frozen too.
 
     :param bool weakref_slot: Make instances weak-referenceable.  This has no
         effect unless ``slots`` is also enabled.
     :param bool auto_attribs: If ``True``, collect `PEP 526`_-annotated
         attributes (Python 3.6 and later only) from the class body.
- 
-        In this case, you **must** annotate every field.  If ``attrs`` 
+
+        In this case, you **must** annotate every field.  If ``attrs``
         encounters a field that is set to an `attr.ib` but lacks a type
         annotation, an `attr.exceptions.UnannotatedAttributeError` is
-        raised.  Use ``field_name: typing.Any = attr.ib(...)`` if you don't 
-        want to set a type. 
- 
-        If you assign a value to those attributes (e.g. ``x: int = 42``), that 
-        value becomes the default value like if it were passed using 
+        raised.  Use ``field_name: typing.Any = attr.ib(...)`` if you don't
+        want to set a type.
+
+        If you assign a value to those attributes (e.g. ``x: int = 42``), that
+        value becomes the default value like if it were passed using
         ``attr.ib(default=42)``.  Passing an instance of `Factory` also
         works as expected in most cases (see warning below).
- 
+
         Attributes annotated as `typing.ClassVar`, and attributes that are
         neither annotated nor set to an `attr.ib` are **ignored**.
- 
+
         .. warning::
            For features that use the attribute name to create decorators (e.g.
            `validators <validators>`), you still *must* assign `attr.ib` to
@@ -1342,7 +1342,7 @@ def attrs(
            These errors can be quite confusing and probably the most common bug
            report on our bug tracker.
 
-        .. _`PEP 526`: https://www.python.org/dev/peps/pep-0526/ 
+        .. _`PEP 526`: https://www.python.org/dev/peps/pep-0526/
     :param bool kw_only: Make all attributes keyword-only (Python 3+)
         in the generated ``__init__`` (if ``init`` is ``False``, this
         parameter is ignored).
@@ -1357,7 +1357,7 @@ def attrs(
         (which implicitly includes any subclass of any exception), the
         following happens to behave like a well-behaved Python exceptions
         class:
- 
+
         - the values for *eq*, *order*, and *hash* are ignored and the
           instances compare and hash by the instance's ids (N.B. ``attrs`` will
           *not* remove existing implementations of ``__hash__`` or the equality
@@ -1407,16 +1407,16 @@ def attrs(
         this, e.g., to automatically add converters or validators to
         fields based on their types.  See `transform-fields` for more details.
 
-    .. versionadded:: 16.0.0 *slots* 
-    .. versionadded:: 16.1.0 *frozen* 
-    .. versionadded:: 16.3.0 *str* 
-    .. versionadded:: 16.3.0 Support for ``__attrs_post_init__``. 
-    .. versionchanged:: 17.1.0 
-       *hash* supports ``None`` as value which is also the default now. 
-    .. versionadded:: 17.3.0 *auto_attribs* 
-    .. versionchanged:: 18.1.0 
-       If *these* is passed, no attributes are deleted from the class body. 
-    .. versionchanged:: 18.1.0 If *these* is ordered, the order is retained. 
+    .. versionadded:: 16.0.0 *slots*
+    .. versionadded:: 16.1.0 *frozen*
+    .. versionadded:: 16.3.0 *str*
+    .. versionadded:: 16.3.0 Support for ``__attrs_post_init__``.
+    .. versionchanged:: 17.1.0
+       *hash* supports ``None`` as value which is also the default now.
+    .. versionadded:: 17.3.0 *auto_attribs*
+    .. versionchanged:: 18.1.0
+       If *these* is passed, no attributes are deleted from the class body.
+    .. versionchanged:: 18.1.0 If *these* is ordered, the order is retained.
     .. versionadded:: 18.2.0 *weakref_slot*
     .. deprecated:: 18.2.0
        ``__lt__``, ``__le__``, ``__gt__``, and ``__ge__`` now raise a
@@ -1440,7 +1440,7 @@ def attrs(
        ``init=False`` injects ``__attrs_init__``
     .. versionchanged:: 21.1.0 Support for ``__attrs_pre_init__``
     .. versionchanged:: 21.1.0 *cmp* undeprecated
-    """ 
+    """
     if auto_detect and PY2:
         raise PythonTooOldError(
             "auto_detect only works on Python 3 and later."
@@ -1452,11 +1452,11 @@ def attrs(
     if isinstance(on_setattr, (list, tuple)):
         on_setattr = setters.pipe(*on_setattr)
 
-    def wrap(cls): 
+    def wrap(cls):
+
+        if getattr(cls, "__class__", None) is None:
+            raise TypeError("attrs only works with new-style classes.")
 
-        if getattr(cls, "__class__", None) is None: 
-            raise TypeError("attrs only works with new-style classes.") 
- 
         is_frozen = frozen or _has_frozen_base_class(cls)
         is_exc = auto_exc is True and issubclass(cls, BaseException)
         has_own_setattr = auto_detect and _has_own_attribute(
@@ -1491,9 +1491,9 @@ def attrs(
         if _determine_whether_to_implement(
             cls, repr, auto_detect, ("__repr__",)
         ):
-            builder.add_repr(repr_ns) 
-        if str is True: 
-            builder.add_str() 
+            builder.add_repr(repr_ns)
+        if str is True:
+            builder.add_str()
 
         eq = _determine_whether_to_implement(
             cls, eq_, auto_detect, ("__eq__", "__ne__")
@@ -1504,7 +1504,7 @@ def attrs(
             cls, order_, auto_detect, ("__lt__", "__le__", "__gt__", "__ge__")
         ):
             builder.add_order()
- 
+
         builder.add_setattr()
 
         if (
@@ -1515,11 +1515,11 @@ def attrs(
             hash = False
         else:
             hash = hash_
-        if hash is not True and hash is not False and hash is not None: 
-            # Can't use `hash in` because 1 == True for example. 
-            raise TypeError( 
-                "Invalid value for hash.  Must be True, False, or None." 
-            ) 
+        if hash is not True and hash is not False and hash is not None:
+            # Can't use `hash in` because 1 == True for example.
+            raise TypeError(
+                "Invalid value for hash.  Must be True, False, or None."
+            )
         elif hash is False or (hash is None and eq is False) or is_exc:
             # Don't do anything. Should fall back to __object__'s __hash__
             # which is by id.
@@ -1533,8 +1533,8 @@ def attrs(
             hash is None and eq is True and is_frozen is True
         ):
             # Build a __hash__ if told so, or if it's safe.
-            builder.add_hash() 
-        else: 
+            builder.add_hash()
+        else:
             # Raise TypeError on attempts to hash.
             if cache_hash:
                 raise TypeError(
@@ -1542,12 +1542,12 @@ def attrs(
                     " hashing must be either explicitly or implicitly "
                     "enabled."
                 )
-            builder.make_unhashable() 
- 
+            builder.make_unhashable()
+
         if _determine_whether_to_implement(
             cls, init, auto_detect, ("__init__",)
         ):
-            builder.add_init() 
+            builder.add_init()
         else:
             builder.add_attrs_init()
             if cache_hash:
@@ -1555,48 +1555,48 @@ def attrs(
                     "Invalid value for cache_hash.  To use hash caching,"
                     " init must be True."
                 )
- 
-        return builder.build_class() 
- 
-    # maybe_cls's type depends on the usage of the decorator.  It's a class 
-    # if it's used as `@attrs` but ``None`` if used as `@attrs()`. 
-    if maybe_cls is None: 
-        return wrap 
-    else: 
-        return wrap(maybe_cls) 
- 
- 
-_attrs = attrs 
-""" 
-Internal alias so we can use it in functions that take an argument called 
-*attrs*. 
-""" 
- 
- 
-if PY2: 
+
+        return builder.build_class()
+
+    # maybe_cls's type depends on the usage of the decorator.  It's a class
+    # if it's used as `@attrs` but ``None`` if used as `@attrs()`.
+    if maybe_cls is None:
+        return wrap
+    else:
+        return wrap(maybe_cls)
+
+
+_attrs = attrs
+"""
+Internal alias so we can use it in functions that take an argument called
+*attrs*.
+"""
+
+
+if PY2:
 
     def _has_frozen_base_class(cls):
-        """ 
-        Check whether *cls* has a frozen ancestor by looking at its 
-        __setattr__. 
-        """ 
-        return ( 
+        """
+        Check whether *cls* has a frozen ancestor by looking at its
+        __setattr__.
+        """
+        return (
             getattr(cls.__setattr__, "__module__", None)
             == _frozen_setattrs.__module__
             and cls.__setattr__.__name__ == _frozen_setattrs.__name__
-        ) 
+        )
 
 
-else: 
+else:
 
     def _has_frozen_base_class(cls):
-        """ 
-        Check whether *cls* has a frozen ancestor by looking at its 
-        __setattr__. 
-        """ 
-        return cls.__setattr__ == _frozen_setattrs 
- 
- 
+        """
+        Check whether *cls* has a frozen ancestor by looking at its
+        __setattr__.
+        """
+        return cls.__setattr__ == _frozen_setattrs
+
+
 def _generate_unique_filename(cls, func_name):
     """
     Create a "filename" suitable for a function being generated.
@@ -1628,15 +1628,15 @@ def _generate_unique_filename(cls, func_name):
 
 
 def _make_hash(cls, attrs, frozen, cache_hash):
-    attrs = tuple( 
+    attrs = tuple(
         a for a in attrs if a.hash is True or (a.hash is None and a.eq is True)
-    ) 
- 
+    )
+
     tab = "        "
 
     unique_filename = _generate_unique_filename(cls, "hash")
-    type_hash = hash(unique_filename) 
- 
+    type_hash = hash(unique_filename)
+
     hash_def = "def __hash__(self"
     hash_func = "hash(("
     closing_braces = "))"
@@ -1645,7 +1645,7 @@ def _make_hash(cls, attrs, frozen, cache_hash):
     else:
         if not PY2:
             hash_def += ", *"
- 
+
         hash_def += (
             ", _cache_wrapper="
             + "__import__('attr._make')._make._CacheHashWrapper):"
@@ -1691,21 +1691,21 @@ def _make_hash(cls, attrs, frozen, cache_hash):
 
     script = "\n".join(method_lines)
     return _make_method("__hash__", script, unique_filename)
- 
- 
-def _add_hash(cls, attrs): 
-    """ 
-    Add a hash method to *cls*. 
-    """ 
+
+
+def _add_hash(cls, attrs):
+    """
+    Add a hash method to *cls*.
+    """
     cls.__hash__ = _make_hash(cls, attrs, frozen=False, cache_hash=False)
-    return cls 
- 
- 
+    return cls
+
+
 def _make_ne():
-    """ 
+    """
     Create __ne__ method.
-    """ 
- 
+    """
+
     def __ne__(self, other):
         """
         Check equality and either forward a NotImplemented or
@@ -1714,9 +1714,9 @@ def _make_ne():
         result = self.__eq__(other)
         if result is NotImplemented:
             return NotImplemented
- 
+
         return not result
- 
+
     return __ne__
 
 
@@ -1727,19 +1727,19 @@ def _make_eq(cls, attrs):
     attrs = [a for a in attrs if a.eq]
 
     unique_filename = _generate_unique_filename(cls, "eq")
-    lines = [ 
-        "def __eq__(self, other):", 
-        "    if other.__class__ is not self.__class__:", 
-        "        return NotImplemented", 
-    ] 
-
-    # We can't just do a big self.x = other.x and... clause due to 
-    # irregularities like nan == nan is false but (nan,) == (nan,) is true. 
+    lines = [
+        "def __eq__(self, other):",
+        "    if other.__class__ is not self.__class__:",
+        "        return NotImplemented",
+    ]
+
+    # We can't just do a big self.x = other.x and... clause due to
+    # irregularities like nan == nan is false but (nan,) == (nan,) is true.
     globs = {}
-    if attrs: 
-        lines.append("    return  (") 
+    if attrs:
+        lines.append("    return  (")
         others = ["    ) == ("]
-        for a in attrs: 
+        for a in attrs:
             if a.eq_key:
                 cmp_name = "_%s_key" % (a.name,)
                 # Add the key function to the global namespace
@@ -1762,15 +1762,15 @@ def _make_eq(cls, attrs):
             else:
                 lines.append("        self.%s," % (a.name,))
                 others.append("        other.%s," % (a.name,))
- 
-        lines += others + ["    )"] 
-    else: 
-        lines.append("    return True") 
- 
-    script = "\n".join(lines) 
- 
+
+        lines += others + ["    )"]
+    else:
+        lines.append("    return True")
+
+    script = "\n".join(lines)
+
     return _make_method("__eq__", script, unique_filename, globs)
- 
+
 
 def _make_order(cls, attrs):
     """
@@ -1778,78 +1778,78 @@ def _make_order(cls, attrs):
     """
     attrs = [a for a in attrs if a.order]
 
-    def attrs_to_tuple(obj): 
-        """ 
-        Save us some typing. 
-        """ 
+    def attrs_to_tuple(obj):
+        """
+        Save us some typing.
+        """
         return tuple(
             key(value) if key else value
             for value, key in (
                 (getattr(obj, a.name), a.order_key) for a in attrs
             )
         )
- 
-    def __lt__(self, other): 
-        """ 
-        Automatically created by attrs. 
-        """ 
+
+    def __lt__(self, other):
+        """
+        Automatically created by attrs.
+        """
         if other.__class__ is self.__class__:
-            return attrs_to_tuple(self) < attrs_to_tuple(other) 
- 
+            return attrs_to_tuple(self) < attrs_to_tuple(other)
+
         return NotImplemented
 
-    def __le__(self, other): 
-        """ 
-        Automatically created by attrs. 
-        """ 
+    def __le__(self, other):
+        """
+        Automatically created by attrs.
+        """
         if other.__class__ is self.__class__:
-            return attrs_to_tuple(self) <= attrs_to_tuple(other) 
- 
+            return attrs_to_tuple(self) <= attrs_to_tuple(other)
+
         return NotImplemented
 
-    def __gt__(self, other): 
-        """ 
-        Automatically created by attrs. 
-        """ 
+    def __gt__(self, other):
+        """
+        Automatically created by attrs.
+        """
         if other.__class__ is self.__class__:
-            return attrs_to_tuple(self) > attrs_to_tuple(other) 
- 
+            return attrs_to_tuple(self) > attrs_to_tuple(other)
+
         return NotImplemented
 
-    def __ge__(self, other): 
-        """ 
-        Automatically created by attrs. 
-        """ 
+    def __ge__(self, other):
+        """
+        Automatically created by attrs.
+        """
         if other.__class__ is self.__class__:
-            return attrs_to_tuple(self) >= attrs_to_tuple(other) 
- 
+            return attrs_to_tuple(self) >= attrs_to_tuple(other)
+
         return NotImplemented
- 
+
     return __lt__, __le__, __gt__, __ge__
- 
+
 
 def _add_eq(cls, attrs=None):
-    """ 
+    """
     Add equality methods to *cls* with *attrs*.
-    """ 
-    if attrs is None: 
-        attrs = cls.__attrs_attrs__ 
- 
+    """
+    if attrs is None:
+        attrs = cls.__attrs_attrs__
+
     cls.__eq__ = _make_eq(cls, attrs)
     cls.__ne__ = _make_ne()
- 
-    return cls 
- 
- 
-_already_repring = threading.local() 
- 
- 
-def _make_repr(attrs, ns): 
-    """ 
+
+    return cls
+
+
+_already_repring = threading.local()
+
+
+def _make_repr(attrs, ns):
+    """
     Make a repr method that includes relevant *attrs*, adding *ns* to the full
     name.
-    """ 
- 
+    """
+
     # Figure out which attributes to include, and which function to use to
     # format them. The a.repr value can be either bool or a custom callable.
     attr_names_with_reprs = tuple(
@@ -1858,146 +1858,146 @@ def _make_repr(attrs, ns):
         if a.repr is not False
     )
 
-    def __repr__(self): 
-        """ 
-        Automatically created by attrs. 
-        """ 
-        try: 
-            working_set = _already_repring.working_set 
-        except AttributeError: 
-            working_set = set() 
-            _already_repring.working_set = working_set 
- 
-        if id(self) in working_set: 
-            return "..." 
-        real_cls = self.__class__ 
-        if ns is None: 
-            qualname = getattr(real_cls, "__qualname__", None) 
-            if qualname is not None: 
-                class_name = qualname.rsplit(">.", 1)[-1] 
-            else: 
-                class_name = real_cls.__name__ 
-        else: 
-            class_name = ns + "." + real_cls.__name__ 
- 
-        # Since 'self' remains on the stack (i.e.: strongly referenced) for the 
-        # duration of this call, it's safe to depend on id(...) stability, and 
-        # not need to track the instance and therefore worry about properties 
-        # like weakref- or hash-ability. 
-        working_set.add(id(self)) 
-        try: 
-            result = [class_name, "("] 
-            first = True 
+    def __repr__(self):
+        """
+        Automatically created by attrs.
+        """
+        try:
+            working_set = _already_repring.working_set
+        except AttributeError:
+            working_set = set()
+            _already_repring.working_set = working_set
+
+        if id(self) in working_set:
+            return "..."
+        real_cls = self.__class__
+        if ns is None:
+            qualname = getattr(real_cls, "__qualname__", None)
+            if qualname is not None:
+                class_name = qualname.rsplit(">.", 1)[-1]
+            else:
+                class_name = real_cls.__name__
+        else:
+            class_name = ns + "." + real_cls.__name__
+
+        # Since 'self' remains on the stack (i.e.: strongly referenced) for the
+        # duration of this call, it's safe to depend on id(...) stability, and
+        # not need to track the instance and therefore worry about properties
+        # like weakref- or hash-ability.
+        working_set.add(id(self))
+        try:
+            result = [class_name, "("]
+            first = True
             for name, attr_repr in attr_names_with_reprs:
-                if first: 
-                    first = False 
-                else: 
-                    result.append(", ") 
+                if first:
+                    first = False
+                else:
+                    result.append(", ")
                 result.extend(
                     (name, "=", attr_repr(getattr(self, name, NOTHING)))
                 )
-            return "".join(result) + ")" 
-        finally: 
-            working_set.remove(id(self)) 
-
-    return __repr__ 
- 
- 
-def _add_repr(cls, ns=None, attrs=None): 
-    """ 
-    Add a repr method to *cls*. 
-    """ 
-    if attrs is None: 
-        attrs = cls.__attrs_attrs__ 
- 
-    cls.__repr__ = _make_repr(attrs, ns) 
-    return cls 
- 
- 
-def fields(cls): 
-    """ 
-    Return the tuple of ``attrs`` attributes for a class. 
- 
-    The tuple also allows accessing the fields by their names (see below for 
-    examples). 
- 
-    :param type cls: Class to introspect. 
- 
-    :raise TypeError: If *cls* is not a class. 
-    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs`` 
-        class. 
- 
+            return "".join(result) + ")"
+        finally:
+            working_set.remove(id(self))
+
+    return __repr__
+
+
+def _add_repr(cls, ns=None, attrs=None):
+    """
+    Add a repr method to *cls*.
+    """
+    if attrs is None:
+        attrs = cls.__attrs_attrs__
+
+    cls.__repr__ = _make_repr(attrs, ns)
+    return cls
+
+
+def fields(cls):
+    """
+    Return the tuple of ``attrs`` attributes for a class.
+
+    The tuple also allows accessing the fields by their names (see below for
+    examples).
+
+    :param type cls: Class to introspect.
+
+    :raise TypeError: If *cls* is not a class.
+    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
+        class.
+
     :rtype: tuple (with name accessors) of `attr.Attribute`
- 
-    ..  versionchanged:: 16.2.0 Returned tuple allows accessing the fields 
-        by name. 
-    """ 
-    if not isclass(cls): 
-        raise TypeError("Passed object must be a class.") 
-    attrs = getattr(cls, "__attrs_attrs__", None) 
-    if attrs is None: 
-        raise NotAnAttrsClassError( 
-            "{cls!r} is not an attrs-decorated class.".format(cls=cls) 
-        ) 
-    return attrs 
- 
- 
-def fields_dict(cls): 
-    """ 
-    Return an ordered dictionary of ``attrs`` attributes for a class, whose 
-    keys are the attribute names. 
- 
-    :param type cls: Class to introspect. 
- 
-    :raise TypeError: If *cls* is not a class. 
-    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs`` 
-        class. 
- 
-    :rtype: an ordered dict where keys are attribute names and values are 
+
+    ..  versionchanged:: 16.2.0 Returned tuple allows accessing the fields
+        by name.
+    """
+    if not isclass(cls):
+        raise TypeError("Passed object must be a class.")
+    attrs = getattr(cls, "__attrs_attrs__", None)
+    if attrs is None:
+        raise NotAnAttrsClassError(
+            "{cls!r} is not an attrs-decorated class.".format(cls=cls)
+        )
+    return attrs
+
+
+def fields_dict(cls):
+    """
+    Return an ordered dictionary of ``attrs`` attributes for a class, whose
+    keys are the attribute names.
+
+    :param type cls: Class to introspect.
+
+    :raise TypeError: If *cls* is not a class.
+    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
+        class.
+
+    :rtype: an ordered dict where keys are attribute names and values are
         `attr.Attribute`\\ s. This will be a `dict` if it's
-        naturally ordered like on Python 3.6+ or an 
-        :class:`~collections.OrderedDict` otherwise. 
- 
-    .. versionadded:: 18.1.0 
-    """ 
-    if not isclass(cls): 
-        raise TypeError("Passed object must be a class.") 
-    attrs = getattr(cls, "__attrs_attrs__", None) 
-    if attrs is None: 
-        raise NotAnAttrsClassError( 
-            "{cls!r} is not an attrs-decorated class.".format(cls=cls) 
-        ) 
-    return ordered_dict(((a.name, a) for a in attrs)) 
- 
- 
-def validate(inst): 
-    """ 
-    Validate all attributes on *inst* that have a validator. 
- 
-    Leaves all exceptions through. 
- 
-    :param inst: Instance of a class with ``attrs`` attributes. 
-    """ 
-    if _config._run_validators is False: 
-        return 
- 
-    for a in fields(inst.__class__): 
-        v = a.validator 
-        if v is not None: 
-            v(inst, a, getattr(inst, a.name)) 
- 
- 
-def _is_slot_cls(cls): 
-    return "__slots__" in cls.__dict__ 
- 
- 
+        naturally ordered like on Python 3.6+ or an
+        :class:`~collections.OrderedDict` otherwise.
+
+    .. versionadded:: 18.1.0
+    """
+    if not isclass(cls):
+        raise TypeError("Passed object must be a class.")
+    attrs = getattr(cls, "__attrs_attrs__", None)
+    if attrs is None:
+        raise NotAnAttrsClassError(
+            "{cls!r} is not an attrs-decorated class.".format(cls=cls)
+        )
+    return ordered_dict(((a.name, a) for a in attrs))
+
+
+def validate(inst):
+    """
+    Validate all attributes on *inst* that have a validator.
+
+    Leaves all exceptions through.
+
+    :param inst: Instance of a class with ``attrs`` attributes.
+    """
+    if _config._run_validators is False:
+        return
+
+    for a in fields(inst.__class__):
+        v = a.validator
+        if v is not None:
+            v(inst, a, getattr(inst, a.name))
+
+
+def _is_slot_cls(cls):
+    return "__slots__" in cls.__dict__
+
+
 def _is_slot_attr(a_name, base_attr_map):
-    """ 
-    Check if the attribute name comes from a slot class. 
-    """ 
+    """
+    Check if the attribute name comes from a slot class.
+    """
     return a_name in base_attr_map and _is_slot_cls(base_attr_map[a_name])
- 
- 
+
+
 def _make_init(
     cls,
     attrs,
@@ -2186,15 +2186,15 @@ def _attrs_to_init_script(
     has_global_on_setattr,
     attrs_init,
 ):
-    """ 
-    Return a script of an initializer for *attrs* and a dict of globals. 
- 
-    The globals are expected by the generated script. 
- 
-    If *frozen* is True, we cannot set the attributes directly so we use 
-    a cached ``object.__setattr__``. 
-    """ 
-    lines = [] 
+    """
+    Return a script of an initializer for *attrs* and a dict of globals.
+
+    The globals are expected by the generated script.
+
+    If *frozen* is True, we cannot set the attributes directly so we use
+    a cached ``object.__setattr__``.
+    """
+    lines = []
     if pre_init:
         lines.append("self.__attrs_pre_init__()")
 
@@ -2206,21 +2206,21 @@ def _attrs_to_init_script(
             "_setattr = _cached_setattr.__get__(self, self.__class__)"
         )
 
-    if frozen is True: 
-        if slots is True: 
+    if frozen is True:
+        if slots is True:
             fmt_setter = _setattr
             fmt_setter_with_converter = _setattr_with_converter
-        else: 
-            # Dict frozen classes assign directly to __dict__. 
-            # But only if the attribute doesn't come from an ancestor slot 
-            # class. 
+        else:
+            # Dict frozen classes assign directly to __dict__.
+            # But only if the attribute doesn't come from an ancestor slot
+            # class.
             # Note _inst_dict will be used again below if cache_hash is True
             lines.append("_inst_dict = self.__dict__")
- 
+
             def fmt_setter(attr_name, value_var, has_on_setattr):
                 if _is_slot_attr(attr_name, base_attr_map):
                     return _setattr(attr_name, value_var, has_on_setattr)
- 
+
                 return "_inst_dict['%s'] = %s" % (attr_name, value_var)
 
             def fmt_setter_with_converter(
@@ -2237,40 +2237,40 @@ def _attrs_to_init_script(
                     value_var,
                 )
 
-    else: 
-        # Not frozen. 
+    else:
+        # Not frozen.
         fmt_setter = _assign
         fmt_setter_with_converter = _assign_with_converter
- 
-    args = [] 
+
+    args = []
     kw_only_args = []
-    attrs_to_validate = [] 
- 
-    # This is a dictionary of names to validator and converter callables. 
-    # Injecting this into __init__ globals lets us avoid lookups. 
-    names_for_globals = {} 
+    attrs_to_validate = []
+
+    # This is a dictionary of names to validator and converter callables.
+    # Injecting this into __init__ globals lets us avoid lookups.
+    names_for_globals = {}
     annotations = {"return": None}
- 
-    for a in attrs: 
-        if a.validator: 
-            attrs_to_validate.append(a) 
 
-        attr_name = a.name 
+    for a in attrs:
+        if a.validator:
+            attrs_to_validate.append(a)
+
+        attr_name = a.name
         has_on_setattr = a.on_setattr is not None or (
             a.on_setattr is not setters.NO_OP and has_global_on_setattr
         )
-        arg_name = a.name.lstrip("_") 
-
-        has_factory = isinstance(a.default, Factory) 
-        if has_factory and a.default.takes_self: 
-            maybe_self = "self" 
-        else: 
-            maybe_self = "" 
-
-        if a.init is False: 
-            if has_factory: 
-                init_factory_name = _init_factory_pat.format(a.name) 
-                if a.converter is not None: 
+        arg_name = a.name.lstrip("_")
+
+        has_factory = isinstance(a.default, Factory)
+        if has_factory and a.default.takes_self:
+            maybe_self = "self"
+        else:
+            maybe_self = ""
+
+        if a.init is False:
+            if has_factory:
+                init_factory_name = _init_factory_pat.format(a.name)
+                if a.converter is not None:
                     lines.append(
                         fmt_setter_with_converter(
                             attr_name,
@@ -2279,8 +2279,8 @@ def _attrs_to_init_script(
                         )
                     )
                     conv_name = _init_converter_pat % (a.name,)
-                    names_for_globals[conv_name] = a.converter 
-                else: 
+                    names_for_globals[conv_name] = a.converter
+                else:
                     lines.append(
                         fmt_setter(
                             attr_name,
@@ -2288,9 +2288,9 @@ def _attrs_to_init_script(
                             has_on_setattr,
                         )
                     )
-                names_for_globals[init_factory_name] = a.default.factory 
-            else: 
-                if a.converter is not None: 
+                names_for_globals[init_factory_name] = a.default.factory
+            else:
+                if a.converter is not None:
                     lines.append(
                         fmt_setter_with_converter(
                             attr_name,
@@ -2299,8 +2299,8 @@ def _attrs_to_init_script(
                         )
                     )
                     conv_name = _init_converter_pat % (a.name,)
-                    names_for_globals[conv_name] = a.converter 
-                else: 
+                    names_for_globals[conv_name] = a.converter
+                else:
                     lines.append(
                         fmt_setter(
                             attr_name,
@@ -2308,14 +2308,14 @@ def _attrs_to_init_script(
                             has_on_setattr,
                         )
                     )
-        elif a.default is not NOTHING and not has_factory: 
+        elif a.default is not NOTHING and not has_factory:
             arg = "%s=attr_dict['%s'].default" % (arg_name, attr_name)
             if a.kw_only:
                 kw_only_args.append(arg)
             else:
                 args.append(arg)
 
-            if a.converter is not None: 
+            if a.converter is not None:
                 lines.append(
                     fmt_setter_with_converter(
                         attr_name, arg_name, has_on_setattr
@@ -2324,10 +2324,10 @@ def _attrs_to_init_script(
                 names_for_globals[
                     _init_converter_pat % (a.name,)
                 ] = a.converter
-            else: 
+            else:
                 lines.append(fmt_setter(attr_name, arg_name, has_on_setattr))
 
-        elif has_factory: 
+        elif has_factory:
             arg = "%s=NOTHING" % (arg_name,)
             if a.kw_only:
                 kw_only_args.append(arg)
@@ -2335,15 +2335,15 @@ def _attrs_to_init_script(
                 args.append(arg)
             lines.append("if %s is not NOTHING:" % (arg_name,))
 
-            init_factory_name = _init_factory_pat.format(a.name) 
-            if a.converter is not None: 
+            init_factory_name = _init_factory_pat.format(a.name)
+            if a.converter is not None:
                 lines.append(
                     "    "
                     + fmt_setter_with_converter(
                         attr_name, arg_name, has_on_setattr
                     )
                 )
-                lines.append("else:") 
+                lines.append("else:")
                 lines.append(
                     "    "
                     + fmt_setter_with_converter(
@@ -2351,15 +2351,15 @@ def _attrs_to_init_script(
                         init_factory_name + "(" + maybe_self + ")",
                         has_on_setattr,
                     )
-                ) 
+                )
                 names_for_globals[
                     _init_converter_pat % (a.name,)
                 ] = a.converter
-            else: 
+            else:
                 lines.append(
                     "    " + fmt_setter(attr_name, arg_name, has_on_setattr)
                 )
-                lines.append("else:") 
+                lines.append("else:")
                 lines.append(
                     "    "
                     + fmt_setter(
@@ -2368,14 +2368,14 @@ def _attrs_to_init_script(
                         has_on_setattr,
                     )
                 )
-            names_for_globals[init_factory_name] = a.default.factory 
-        else: 
+            names_for_globals[init_factory_name] = a.default.factory
+        else:
             if a.kw_only:
                 kw_only_args.append(arg_name)
             else:
                 args.append(arg_name)
 
-            if a.converter is not None: 
+            if a.converter is not None:
                 lines.append(
                     fmt_setter_with_converter(
                         attr_name, arg_name, has_on_setattr
@@ -2384,9 +2384,9 @@ def _attrs_to_init_script(
                 names_for_globals[
                     _init_converter_pat % (a.name,)
                 ] = a.converter
-            else: 
+            else:
                 lines.append(fmt_setter(attr_name, arg_name, has_on_setattr))
- 
+
         if a.init is True:
             if a.type is not None and a.converter is None:
                 annotations[arg_name] = a.type
@@ -2405,22 +2405,22 @@ def _attrs_to_init_script(
                         is not inspect.Parameter.empty
                     ):
                         annotations[arg_name] = sig_params[0].annotation
- 
-    if attrs_to_validate:  # we can skip this if there are no validators. 
-        names_for_globals["_config"] = _config 
-        lines.append("if _config._run_validators is True:") 
-        for a in attrs_to_validate: 
+
+    if attrs_to_validate:  # we can skip this if there are no validators.
+        names_for_globals["_config"] = _config
+        lines.append("if _config._run_validators is True:")
+        for a in attrs_to_validate:
             val_name = "__attr_validator_" + a.name
             attr_name = "__attr_" + a.name
             lines.append(
                 "    %s(self, %s, self.%s)" % (val_name, attr_name, a.name)
             )
-            names_for_globals[val_name] = a.validator 
-            names_for_globals[attr_name] = a 
+            names_for_globals[val_name] = a.validator
+            names_for_globals[attr_name] = a
+
+    if post_init:
+        lines.append("self.__attrs_post_init__()")
 
-    if post_init: 
-        lines.append("self.__attrs_post_init__()") 
- 
     # because this is set only after __attrs_post_init is called, a crash
     # will result if post-init tries to access the hash code.  This seemed
     # preferable to setting this beforehand, in which case alteration to
@@ -2459,8 +2459,8 @@ def _attrs_to_init_script(
     return (
         """\
 def {init_name}(self, {args}):
-    {lines} 
-""".format( 
+    {lines}
+""".format(
             init_name=("__attrs_init__" if attrs_init else "__init__"),
             args=args,
             lines="\n    ".join(lines) if lines else "pass",
@@ -2468,12 +2468,12 @@ def {init_name}(self, {args}):
         names_for_globals,
         annotations,
     )
- 
- 
-class Attribute(object): 
-    """ 
-    *Read-only* representation of an attribute. 
- 
+
+
+class Attribute(object):
+    """
+    *Read-only* representation of an attribute.
+
     Instances of this class are frequently used for introspection purposes
     like:
 
@@ -2481,13 +2481,13 @@ class Attribute(object):
     - Validators get them passed as the first argument.
     - The *field transformer* hook receives a list of them.
 
-    :attribute name: The name of the attribute. 
+    :attribute name: The name of the attribute.
     :attribute inherited: Whether or not that attribute has been inherited from
         a base class.
- 
+
     Plus *all* arguments of `attr.ib` (except for ``factory``
     which is only syntactic sugar for ``default=Factory(...)``.
- 
+
     .. versionadded:: 20.1.0 *inherited*
     .. versionadded:: 20.1.0 *on_setattr*
     .. versionchanged:: 20.2.0 *inherited* is not taken into account for
@@ -2495,9 +2495,9 @@ class Attribute(object):
     .. versionadded:: 21.1.0 *eq_key* and *order_key*
 
     For the full version history of the fields, see `attr.ib`.
-    """ 
+    """
 
-    __slots__ = ( 
+    __slots__ = (
         "name",
         "default",
         "validator",
@@ -2514,8 +2514,8 @@ class Attribute(object):
         "kw_only",
         "inherited",
         "on_setattr",
-    ) 
- 
+    )
+
     def __init__(
         self,
         name,
@@ -2540,22 +2540,22 @@ class Attribute(object):
             cmp, eq_key or eq, order_key or order, True
         )
 
-        # Cache this descriptor here to speed things up later. 
-        bound_setattr = _obj_setattr.__get__(self, Attribute) 
- 
-        # Despite the big red warning, people *do* instantiate `Attribute` 
-        # themselves. 
-        bound_setattr("name", name) 
-        bound_setattr("default", default) 
-        bound_setattr("validator", validator) 
-        bound_setattr("repr", repr) 
+        # Cache this descriptor here to speed things up later.
+        bound_setattr = _obj_setattr.__get__(self, Attribute)
+
+        # Despite the big red warning, people *do* instantiate `Attribute`
+        # themselves.
+        bound_setattr("name", name)
+        bound_setattr("default", default)
+        bound_setattr("validator", validator)
+        bound_setattr("repr", repr)
         bound_setattr("eq", eq)
         bound_setattr("eq_key", eq_key)
         bound_setattr("order", order)
         bound_setattr("order_key", order_key)
-        bound_setattr("hash", hash) 
-        bound_setattr("init", init) 
-        bound_setattr("converter", converter) 
+        bound_setattr("hash", hash)
+        bound_setattr("init", init)
+        bound_setattr("converter", converter)
         bound_setattr(
             "metadata",
             (
@@ -2564,25 +2564,25 @@ class Attribute(object):
                 else _empty_metadata_singleton
             ),
         )
-        bound_setattr("type", type) 
+        bound_setattr("type", type)
         bound_setattr("kw_only", kw_only)
         bound_setattr("inherited", inherited)
         bound_setattr("on_setattr", on_setattr)
- 
-    def __setattr__(self, name, value): 
-        raise FrozenInstanceError() 
- 
-    @classmethod 
-    def from_counting_attr(cls, name, ca, type=None): 
-        # type holds the annotated value. deal with conflicts: 
-        if type is None: 
-            type = ca.type 
-        elif ca.type is not None: 
-            raise ValueError( 
-                "Type annotation and type argument cannot both be present" 
-            ) 
-        inst_dict = { 
-            k: getattr(ca, k) 
+
+    def __setattr__(self, name, value):
+        raise FrozenInstanceError()
+
+    @classmethod
+    def from_counting_attr(cls, name, ca, type=None):
+        # type holds the annotated value. deal with conflicts:
+        if type is None:
+            type = ca.type
+        elif ca.type is not None:
+            raise ValueError(
+                "Type annotation and type argument cannot both be present"
+            )
+        inst_dict = {
+            k: getattr(ca, k)
             for k in Attribute.__slots__
             if k
             not in (
@@ -2591,18 +2591,18 @@ class Attribute(object):
                 "default",
                 "type",
                 "inherited",
-            )  # exclude methods and deprecated alias 
-        } 
-        return cls( 
+            )  # exclude methods and deprecated alias
+        }
+        return cls(
             name=name,
             validator=ca._validator,
             default=ca._default,
             type=type,
             cmp=None,
             inherited=False,
-            **inst_dict 
-        ) 
- 
+            **inst_dict
+        )
+
     @property
     def cmp(self):
         """
@@ -2630,37 +2630,37 @@ class Attribute(object):
 
         return new
 
-    # Don't use _add_pickle since fields(Attribute) doesn't work 
-    def __getstate__(self): 
-        """ 
-        Play nice with pickle. 
-        """ 
+    # Don't use _add_pickle since fields(Attribute) doesn't work
+    def __getstate__(self):
+        """
+        Play nice with pickle.
+        """
         return tuple(
             getattr(self, name) if name != "metadata" else dict(self.metadata)
             for name in self.__slots__
         )
- 
-    def __setstate__(self, state): 
-        """ 
-        Play nice with pickle. 
-        """ 
+
+    def __setstate__(self, state):
+        """
+        Play nice with pickle.
+        """
         self._setattrs(zip(self.__slots__, state))
 
     def _setattrs(self, name_values_pairs):
-        bound_setattr = _obj_setattr.__get__(self, Attribute) 
+        bound_setattr = _obj_setattr.__get__(self, Attribute)
         for name, value in name_values_pairs:
-            if name != "metadata": 
-                bound_setattr(name, value) 
-            else: 
+            if name != "metadata":
+                bound_setattr(name, value)
+            else:
                 bound_setattr(
                     name,
                     metadata_proxy(value)
                     if value
                     else _empty_metadata_singleton,
                 )
- 
- 
-_a = [ 
+
+
+_a = [
     Attribute(
         name=name,
         default=NOTHING,
@@ -2673,26 +2673,26 @@ _a = [
         init=True,
         inherited=False,
     )
-    for name in Attribute.__slots__ 
-] 
- 
-Attribute = _add_hash( 
+    for name in Attribute.__slots__
+]
+
+Attribute = _add_hash(
     _add_eq(
         _add_repr(Attribute, attrs=_a),
         attrs=[a for a in _a if a.name != "inherited"],
     ),
     attrs=[a for a in _a if a.hash and a.name != "inherited"],
-) 
- 
- 
-class _CountingAttr(object): 
-    """ 
-    Intermediate representation of attributes that uses a counter to preserve 
-    the order in which the attributes have been defined. 
- 
-    *Internal* data structure of the attrs library.  Running into is most 
-    likely the result of a bug like a forgotten `@attr.s` decorator. 
-    """ 
+)
+
+
+class _CountingAttr(object):
+    """
+    Intermediate representation of attributes that uses a counter to preserve
+    the order in which the attributes have been defined.
+
+    *Internal* data structure of the attrs library.  Running into is most
+    likely the result of a bug like a forgotten `@attr.s` decorator.
+    """
 
     __slots__ = (
         "counter",
@@ -2711,7 +2711,7 @@ class _CountingAttr(object):
         "kw_only",
         "on_setattr",
     )
-    __attrs_attrs__ = tuple( 
+    __attrs_attrs__ = tuple(
         Attribute(
             name=name,
             default=NOTHING,
@@ -2738,7 +2738,7 @@ class _CountingAttr(object):
             "init",
             "on_setattr",
         )
-    ) + ( 
+    ) + (
         Attribute(
             name="metadata",
             default=None,
@@ -2755,9 +2755,9 @@ class _CountingAttr(object):
             inherited=False,
             on_setattr=None,
         ),
-    ) 
-    cls_counter = 0 
- 
+    )
+    cls_counter = 0
+
     def __init__(
         self,
         default,
@@ -2776,89 +2776,89 @@ class _CountingAttr(object):
         order_key,
         on_setattr,
     ):
-        _CountingAttr.cls_counter += 1 
-        self.counter = _CountingAttr.cls_counter 
-        self._default = default 
+        _CountingAttr.cls_counter += 1
+        self.counter = _CountingAttr.cls_counter
+        self._default = default
         self._validator = validator
         self.converter = converter
-        self.repr = repr 
+        self.repr = repr
         self.eq = eq
         self.eq_key = eq_key
         self.order = order
         self.order_key = order_key
-        self.hash = hash 
-        self.init = init 
-        self.metadata = metadata 
-        self.type = type 
+        self.hash = hash
+        self.init = init
+        self.metadata = metadata
+        self.type = type
         self.kw_only = kw_only
         self.on_setattr = on_setattr
- 
-    def validator(self, meth): 
-        """ 
-        Decorator that adds *meth* to the list of validators. 
- 
-        Returns *meth* unchanged. 
- 
-        .. versionadded:: 17.1.0 
-        """ 
-        if self._validator is None: 
-            self._validator = meth 
-        else: 
-            self._validator = and_(self._validator, meth) 
-        return meth 
- 
-    def default(self, meth): 
-        """ 
-        Decorator that allows to set the default for an attribute. 
- 
-        Returns *meth* unchanged. 
- 
-        :raises DefaultAlreadySetError: If default has been set before. 
- 
-        .. versionadded:: 17.1.0 
-        """ 
-        if self._default is not NOTHING: 
-            raise DefaultAlreadySetError() 
- 
-        self._default = Factory(meth, takes_self=True) 
- 
-        return meth 
- 
- 
+
+    def validator(self, meth):
+        """
+        Decorator that adds *meth* to the list of validators.
+
+        Returns *meth* unchanged.
+
+        .. versionadded:: 17.1.0
+        """
+        if self._validator is None:
+            self._validator = meth
+        else:
+            self._validator = and_(self._validator, meth)
+        return meth
+
+    def default(self, meth):
+        """
+        Decorator that allows to set the default for an attribute.
+
+        Returns *meth* unchanged.
+
+        :raises DefaultAlreadySetError: If default has been set before.
+
+        .. versionadded:: 17.1.0
+        """
+        if self._default is not NOTHING:
+            raise DefaultAlreadySetError()
+
+        self._default = Factory(meth, takes_self=True)
+
+        return meth
+
+
 _CountingAttr = _add_eq(_add_repr(_CountingAttr))
- 
- 
-class Factory(object): 
-    """ 
-    Stores a factory callable. 
- 
+
+
+class Factory(object):
+    """
+    Stores a factory callable.
+
     If passed as the default value to `attr.ib`, the factory is used to
-    generate a new value. 
- 
-    :param callable factory: A callable that takes either none or exactly one 
-        mandatory positional argument depending on *takes_self*. 
-    :param bool takes_self: Pass the partially initialized instance that is 
-        being initialized as a positional argument. 
- 
-    .. versionadded:: 17.1.0  *takes_self* 
-    """ 
+    generate a new value.
+
+    :param callable factory: A callable that takes either none or exactly one
+        mandatory positional argument depending on *takes_self*.
+    :param bool takes_self: Pass the partially initialized instance that is
+        being initialized as a positional argument.
+
+    .. versionadded:: 17.1.0  *takes_self*
+    """
 
     __slots__ = ("factory", "takes_self")
- 
-    def __init__(self, factory, takes_self=False): 
-        """ 
-        `Factory` is part of the default machinery so if we want a default 
-        value here, we have to implement it ourselves. 
-        """ 
-        self.factory = factory 
-        self.takes_self = takes_self 
- 
+
+    def __init__(self, factory, takes_self=False):
+        """
+        `Factory` is part of the default machinery so if we want a default
+        value here, we have to implement it ourselves.
+        """
+        self.factory = factory
+        self.takes_self = takes_self
+
     def __getstate__(self):
         """
         Play nice with pickle.
         """
         return tuple(getattr(self, name) for name in self.__slots__)
- 
+
     def __setstate__(self, state):
         """
         Play nice with pickle.
@@ -2886,40 +2886,40 @@ _f = [
 Factory = _add_hash(_add_eq(_add_repr(Factory, attrs=_f), attrs=_f), attrs=_f)
 
 
-def make_class(name, attrs, bases=(object,), **attributes_arguments): 
-    """ 
-    A quick way to create a new class called *name* with *attrs*. 
- 
+def make_class(name, attrs, bases=(object,), **attributes_arguments):
+    """
+    A quick way to create a new class called *name* with *attrs*.
+
     :param str name: The name for the new class.
- 
-    :param attrs: A list of names or a dictionary of mappings of names to 
-        attributes. 
- 
+
+    :param attrs: A list of names or a dictionary of mappings of names to
+        attributes.
+
         If *attrs* is a list or an ordered dict (`dict` on Python 3.6+,
         `collections.OrderedDict` otherwise), the order is deduced from
-        the order of the names or attributes inside *attrs*.  Otherwise the 
-        order of the definition of the attributes is used. 
+        the order of the names or attributes inside *attrs*.  Otherwise the
+        order of the definition of the attributes is used.
     :type attrs: `list` or `dict`
- 
-    :param tuple bases: Classes that the new class will subclass. 
- 
+
+    :param tuple bases: Classes that the new class will subclass.
+
     :param attributes_arguments: Passed unmodified to `attr.s`.
- 
-    :return: A new class with *attrs*. 
-    :rtype: type 
- 
-    .. versionadded:: 17.1.0 *bases* 
-    .. versionchanged:: 18.1.0 If *attrs* is ordered, the order is retained. 
-    """ 
-    if isinstance(attrs, dict): 
-        cls_dict = attrs 
-    elif isinstance(attrs, (list, tuple)): 
-        cls_dict = dict((a, attrib()) for a in attrs) 
-    else: 
-        raise TypeError("attrs argument must be a dict or a list.") 
- 
+
+    :return: A new class with *attrs*.
+    :rtype: type
+
+    .. versionadded:: 17.1.0 *bases*
+    .. versionchanged:: 18.1.0 If *attrs* is ordered, the order is retained.
+    """
+    if isinstance(attrs, dict):
+        cls_dict = attrs
+    elif isinstance(attrs, (list, tuple)):
+        cls_dict = dict((a, attrib()) for a in attrs)
+    else:
+        raise TypeError("attrs argument must be a dict or a list.")
+
     pre_init = cls_dict.pop("__attrs_pre_init__", None)
-    post_init = cls_dict.pop("__attrs_post_init__", None) 
+    post_init = cls_dict.pop("__attrs_post_init__", None)
     user_init = cls_dict.pop("__init__", None)
 
     body = {}
@@ -2932,17 +2932,17 @@ def make_class(name, attrs, bases=(object,), **attributes_arguments):
 
     type_ = new_class(name, bases, {}, lambda ns: ns.update(body))
 
-    # For pickling to work, the __module__ variable needs to be set to the 
-    # frame where the class is created.  Bypass this step in environments where 
-    # sys._getframe is not defined (Jython for example) or sys._getframe is not 
-    # defined for arguments greater than 0 (IronPython). 
-    try: 
-        type_.__module__ = sys._getframe(1).f_globals.get( 
+    # For pickling to work, the __module__ variable needs to be set to the
+    # frame where the class is created.  Bypass this step in environments where
+    # sys._getframe is not defined (Jython for example) or sys._getframe is not
+    # defined for arguments greater than 0 (IronPython).
+    try:
+        type_.__module__ = sys._getframe(1).f_globals.get(
             "__name__", "__main__"
-        ) 
-    except (AttributeError, ValueError): 
-        pass 
- 
+        )
+    except (AttributeError, ValueError):
+        pass
+
     # We do it here for proper warnings with meaningful stacklevel.
     cmp = attributes_arguments.pop("cmp", None)
     (
@@ -2955,45 +2955,45 @@ def make_class(name, attrs, bases=(object,), **attributes_arguments):
         True,
     )
 
-    return _attrs(these=cls_dict, **attributes_arguments)(type_) 
- 
- 
-# These are required by within this module so we define them here and merely 
+    return _attrs(these=cls_dict, **attributes_arguments)(type_)
+
+
+# These are required by within this module so we define them here and merely
 # import into .validators / .converters.
- 
- 
-@attrs(slots=True, hash=True) 
-class _AndValidator(object): 
-    """ 
-    Compose many validators to a single one. 
-    """ 
-
-    _validators = attrib() 
- 
-    def __call__(self, inst, attr, value): 
-        for v in self._validators: 
-            v(inst, attr, value) 
- 
- 
-def and_(*validators): 
-    """ 
-    A validator that composes multiple validators into one. 
- 
-    When called on a value, it runs all wrapped validators. 
- 
+
+
+@attrs(slots=True, hash=True)
+class _AndValidator(object):
+    """
+    Compose many validators to a single one.
+    """
+
+    _validators = attrib()
+
+    def __call__(self, inst, attr, value):
+        for v in self._validators:
+            v(inst, attr, value)
+
+
+def and_(*validators):
+    """
+    A validator that composes multiple validators into one.
+
+    When called on a value, it runs all wrapped validators.
+
     :param callables validators: Arbitrary number of validators.
- 
-    .. versionadded:: 17.1.0 
-    """ 
-    vals = [] 
-    for validator in validators: 
-        vals.extend( 
+
+    .. versionadded:: 17.1.0
+    """
+    vals = []
+    for validator in validators:
+        vals.extend(
             validator._validators
             if isinstance(validator, _AndValidator)
-            else [validator] 
-        ) 
- 
-    return _AndValidator(tuple(vals)) 
+            else [validator]
+        )
+
+    return _AndValidator(tuple(vals))
 
 
 def pipe(*converters):
diff --git a/contrib/python/attrs/attr/converters.py b/contrib/python/attrs/attr/converters.py
index d36652e31c..2777db6d0a 100644
--- a/contrib/python/attrs/attr/converters.py
+++ b/contrib/python/attrs/attr/converters.py
@@ -1,12 +1,12 @@
-""" 
-Commonly useful converters. 
-""" 
- 
-from __future__ import absolute_import, division, print_function 
- 
+"""
+Commonly useful converters.
+"""
+
+from __future__ import absolute_import, division, print_function
+
 from ._compat import PY2
 from ._make import NOTHING, Factory, pipe
- 
+
 
 if not PY2:
     import inspect
@@ -20,25 +20,25 @@ __all__ = [
 ]
 
 
-def optional(converter): 
-    """ 
-    A converter that allows an attribute to be optional. An optional attribute 
-    is one which can be set to ``None``. 
- 
+def optional(converter):
+    """
+    A converter that allows an attribute to be optional. An optional attribute
+    is one which can be set to ``None``.
+
     Type annotations will be inferred from the wrapped converter's, if it
     has any.
 
-    :param callable converter: the converter that is used for non-``None`` 
-        values. 
- 
+    :param callable converter: the converter that is used for non-``None``
+        values.
+
     .. versionadded:: 17.1.0
-    """ 
- 
-    def optional_converter(val): 
-        if val is None: 
-            return None 
-        return converter(val) 
- 
+    """
+
+    def optional_converter(val):
+        if val is None:
+            return None
+        return converter(val)
+
     if not PY2:
         sig = None
         try:
@@ -56,7 +56,7 @@ def optional(converter):
                     sig.return_annotation
                 ]
 
-    return optional_converter 
+    return optional_converter
 
 
 def default_if_none(default=NOTHING, factory=None):
diff --git a/contrib/python/attrs/attr/exceptions.py b/contrib/python/attrs/attr/exceptions.py
index 3669abab3a..f6f9861bea 100644
--- a/contrib/python/attrs/attr/exceptions.py
+++ b/contrib/python/attrs/attr/exceptions.py
@@ -1,21 +1,21 @@
-from __future__ import absolute_import, division, print_function 
- 
- 
+from __future__ import absolute_import, division, print_function
+
+
 class FrozenError(AttributeError):
-    """ 
+    """
     A frozen/immutable instance or attribute have been attempted to be
     modified.
- 
-    It mirrors the behavior of ``namedtuples`` by using the same error message 
+
+    It mirrors the behavior of ``namedtuples`` by using the same error message
     and subclassing `AttributeError`.
- 
+
     .. versionadded:: 20.1.0
-    """ 
+    """
+
+    msg = "can't set attribute"
+    args = [msg]
+
 
-    msg = "can't set attribute" 
-    args = [msg] 
- 
- 
 class FrozenInstanceError(FrozenError):
     """
     A frozen instance has been attempted to be modified.
@@ -32,38 +32,38 @@ class FrozenAttributeError(FrozenError):
     """
 
 
-class AttrsAttributeNotFoundError(ValueError): 
-    """ 
-    An ``attrs`` function couldn't find an attribute that the user asked for. 
- 
-    .. versionadded:: 16.2.0 
-    """ 
- 
- 
-class NotAnAttrsClassError(ValueError): 
-    """ 
-    A non-``attrs`` class has been passed into an ``attrs`` function. 
- 
-    .. versionadded:: 16.2.0 
-    """ 
- 
- 
-class DefaultAlreadySetError(RuntimeError): 
-    """ 
-    A default has been set using ``attr.ib()`` and is attempted to be reset 
-    using the decorator. 
- 
-    .. versionadded:: 17.1.0 
-    """ 
- 
- 
-class UnannotatedAttributeError(RuntimeError): 
-    """ 
-    A class with ``auto_attribs=True`` has an ``attr.ib()`` without a type 
-    annotation. 
- 
-    .. versionadded:: 17.3.0 
-    """ 
+class AttrsAttributeNotFoundError(ValueError):
+    """
+    An ``attrs`` function couldn't find an attribute that the user asked for.
+
+    .. versionadded:: 16.2.0
+    """
+
+
+class NotAnAttrsClassError(ValueError):
+    """
+    A non-``attrs`` class has been passed into an ``attrs`` function.
+
+    .. versionadded:: 16.2.0
+    """
+
+
+class DefaultAlreadySetError(RuntimeError):
+    """
+    A default has been set using ``attr.ib()`` and is attempted to be reset
+    using the decorator.
+
+    .. versionadded:: 17.1.0
+    """
+
+
+class UnannotatedAttributeError(RuntimeError):
+    """
+    A class with ``auto_attribs=True`` has an ``attr.ib()`` without a type
+    annotation.
+
+    .. versionadded:: 17.3.0
+    """
 
 
 class PythonTooOldError(RuntimeError):
diff --git a/contrib/python/attrs/attr/filters.py b/contrib/python/attrs/attr/filters.py
index ba8f0482f9..dc47e8fa38 100644
--- a/contrib/python/attrs/attr/filters.py
+++ b/contrib/python/attrs/attr/filters.py
@@ -1,52 +1,52 @@
-""" 
+"""
 Commonly useful filters for `attr.asdict`.
-""" 
- 
-from __future__ import absolute_import, division, print_function 
- 
-from ._compat import isclass 
-from ._make import Attribute 
- 
- 
-def _split_what(what): 
-    """ 
-    Returns a tuple of `frozenset`s of classes and attributes. 
-    """ 
-    return ( 
-        frozenset(cls for cls in what if isclass(cls)), 
-        frozenset(cls for cls in what if isinstance(cls, Attribute)), 
-    ) 
- 
- 
-def include(*what): 
-    """ 
-    Whitelist *what*. 
- 
-    :param what: What to whitelist. 
+"""
+
+from __future__ import absolute_import, division, print_function
+
+from ._compat import isclass
+from ._make import Attribute
+
+
+def _split_what(what):
+    """
+    Returns a tuple of `frozenset`s of classes and attributes.
+    """
+    return (
+        frozenset(cls for cls in what if isclass(cls)),
+        frozenset(cls for cls in what if isinstance(cls, Attribute)),
+    )
+
+
+def include(*what):
+    """
+    Whitelist *what*.
+
+    :param what: What to whitelist.
     :type what: `list` of `type` or `attr.Attribute`\\ s
- 
+
     :rtype: `callable`
-    """ 
-    cls, attrs = _split_what(what) 
- 
-    def include_(attribute, value): 
-        return value.__class__ in cls or attribute in attrs 
- 
-    return include_ 
- 
- 
-def exclude(*what): 
-    """ 
-    Blacklist *what*. 
- 
-    :param what: What to blacklist. 
+    """
+    cls, attrs = _split_what(what)
+
+    def include_(attribute, value):
+        return value.__class__ in cls or attribute in attrs
+
+    return include_
+
+
+def exclude(*what):
+    """
+    Blacklist *what*.
+
+    :param what: What to blacklist.
     :type what: `list` of classes or `attr.Attribute`\\ s.
- 
+
     :rtype: `callable`
-    """ 
-    cls, attrs = _split_what(what) 
- 
-    def exclude_(attribute, value): 
-        return value.__class__ not in cls and attribute not in attrs 
- 
-    return exclude_ 
+    """
+    cls, attrs = _split_what(what)
+
+    def exclude_(attribute, value):
+        return value.__class__ not in cls and attribute not in attrs
+
+    return exclude_
diff --git a/contrib/python/attrs/attr/validators.py b/contrib/python/attrs/attr/validators.py
index 6932bac87a..b9a73054e9 100644
--- a/contrib/python/attrs/attr/validators.py
+++ b/contrib/python/attrs/attr/validators.py
@@ -1,15 +1,15 @@
-""" 
-Commonly useful validators. 
-""" 
- 
-from __future__ import absolute_import, division, print_function 
- 
+"""
+Commonly useful validators.
+"""
+
+from __future__ import absolute_import, division, print_function
+
 import re
 
-from ._make import _AndValidator, and_, attrib, attrs 
+from ._make import _AndValidator, and_, attrib, attrs
 from .exceptions import NotCallableError
- 
- 
+
+
 __all__ = [
     "and_",
     "deep_iterable",
@@ -21,19 +21,19 @@ __all__ = [
     "optional",
     "provides",
 ]
- 
- 
-@attrs(repr=False, slots=True, hash=True) 
-class _InstanceOfValidator(object): 
-    type = attrib() 
- 
-    def __call__(self, inst, attr, value): 
-        """ 
-        We use a callable class to be able to change the ``__repr__``. 
-        """ 
-        if not isinstance(value, self.type): 
-            raise TypeError( 
-                "'{name}' must be {type!r} (got {value!r} that is a " 
+
+
+@attrs(repr=False, slots=True, hash=True)
+class _InstanceOfValidator(object):
+    type = attrib()
+
+    def __call__(self, inst, attr, value):
+        """
+        We use a callable class to be able to change the ``__repr__``.
+        """
+        if not isinstance(value, self.type):
+            raise TypeError(
+                "'{name}' must be {type!r} (got {value!r} that is a "
                 "{actual!r}).".format(
                     name=attr.name,
                     type=self.type,
@@ -43,30 +43,30 @@ class _InstanceOfValidator(object):
                 attr,
                 self.type,
                 value,
-            ) 
- 
-    def __repr__(self): 
+            )
+
+    def __repr__(self):
         return "<instance_of validator for type {type!r}>".format(
             type=self.type
-        ) 
- 
- 
-def instance_of(type): 
-    """ 
+        )
+
+
+def instance_of(type):
+    """
     A validator that raises a `TypeError` if the initializer is called
-    with a wrong type for this particular attribute (checks are performed using 
+    with a wrong type for this particular attribute (checks are performed using
     `isinstance` therefore it's also valid to pass a tuple of types).
- 
-    :param type: The type to check for. 
-    :type type: type or tuple of types 
- 
-    :raises TypeError: With a human readable error message, the attribute 
+
+    :param type: The type to check for.
+    :type type: type or tuple of types
+
+    :raises TypeError: With a human readable error message, the attribute
         (of type `attr.Attribute`), the expected type, and the value it
-        got. 
-    """ 
-    return _InstanceOfValidator(type) 
- 
- 
+        got.
+    """
+    return _InstanceOfValidator(type)
+
+
 @attrs(repr=False, frozen=True, slots=True)
 class _MatchesReValidator(object):
     regex = attrib()
@@ -139,121 +139,121 @@ def matches_re(regex, flags=0, func=None):
     return _MatchesReValidator(pattern, flags, match_func)
 
 
-@attrs(repr=False, slots=True, hash=True) 
-class _ProvidesValidator(object): 
-    interface = attrib() 
- 
-    def __call__(self, inst, attr, value): 
-        """ 
-        We use a callable class to be able to change the ``__repr__``. 
-        """ 
-        if not self.interface.providedBy(value): 
-            raise TypeError( 
-                "'{name}' must provide {interface!r} which {value!r} " 
+@attrs(repr=False, slots=True, hash=True)
+class _ProvidesValidator(object):
+    interface = attrib()
+
+    def __call__(self, inst, attr, value):
+        """
+        We use a callable class to be able to change the ``__repr__``.
+        """
+        if not self.interface.providedBy(value):
+            raise TypeError(
+                "'{name}' must provide {interface!r} which {value!r} "
                 "doesn't.".format(
                     name=attr.name, interface=self.interface, value=value
                 ),
                 attr,
                 self.interface,
                 value,
-            ) 
- 
-    def __repr__(self): 
+            )
+
+    def __repr__(self):
         return "<provides validator for interface {interface!r}>".format(
             interface=self.interface
-        ) 
- 
- 
-def provides(interface): 
-    """ 
+        )
+
+
+def provides(interface):
+    """
     A validator that raises a `TypeError` if the initializer is called
-    with an object that does not provide the requested *interface* (checks are 
-    performed using ``interface.providedBy(value)`` (see `zope.interface 
-    <https://zopeinterface.readthedocs.io/en/latest/>`_). 
- 
+    with an object that does not provide the requested *interface* (checks are
+    performed using ``interface.providedBy(value)`` (see `zope.interface
+    <https://zopeinterface.readthedocs.io/en/latest/>`_).
+
     :param interface: The interface to check for.
     :type interface: ``zope.interface.Interface``
- 
-    :raises TypeError: With a human readable error message, the attribute 
+
+    :raises TypeError: With a human readable error message, the attribute
         (of type `attr.Attribute`), the expected interface, and the
-        value it got. 
-    """ 
-    return _ProvidesValidator(interface) 
- 
- 
-@attrs(repr=False, slots=True, hash=True) 
-class _OptionalValidator(object): 
-    validator = attrib() 
- 
-    def __call__(self, inst, attr, value): 
-        if value is None: 
-            return 
- 
-        self.validator(inst, attr, value) 
- 
-    def __repr__(self): 
+        value it got.
+    """
+    return _ProvidesValidator(interface)
+
+
+@attrs(repr=False, slots=True, hash=True)
+class _OptionalValidator(object):
+    validator = attrib()
+
+    def __call__(self, inst, attr, value):
+        if value is None:
+            return
+
+        self.validator(inst, attr, value)
+
+    def __repr__(self):
         return "<optional validator for {what} or None>".format(
             what=repr(self.validator)
-        ) 
- 
- 
-def optional(validator): 
-    """ 
-    A validator that makes an attribute optional.  An optional attribute is one 
-    which can be set to ``None`` in addition to satisfying the requirements of 
-    the sub-validator. 
- 
-    :param validator: A validator (or a list of validators) that is used for 
-        non-``None`` values. 
+        )
+
+
+def optional(validator):
+    """
+    A validator that makes an attribute optional.  An optional attribute is one
+    which can be set to ``None`` in addition to satisfying the requirements of
+    the sub-validator.
+
+    :param validator: A validator (or a list of validators) that is used for
+        non-``None`` values.
     :type validator: callable or `list` of callables.
- 
-    .. versionadded:: 15.1.0 
-    .. versionchanged:: 17.1.0 *validator* can be a list of validators. 
-    """ 
-    if isinstance(validator, list): 
-        return _OptionalValidator(_AndValidator(validator)) 
-    return _OptionalValidator(validator) 
- 
- 
-@attrs(repr=False, slots=True, hash=True) 
-class _InValidator(object): 
-    options = attrib() 
- 
-    def __call__(self, inst, attr, value): 
+
+    .. versionadded:: 15.1.0
+    .. versionchanged:: 17.1.0 *validator* can be a list of validators.
+    """
+    if isinstance(validator, list):
+        return _OptionalValidator(_AndValidator(validator))
+    return _OptionalValidator(validator)
+
+
+@attrs(repr=False, slots=True, hash=True)
+class _InValidator(object):
+    options = attrib()
+
+    def __call__(self, inst, attr, value):
         try:
             in_options = value in self.options
         except TypeError:  # e.g. `1 in "abc"`
             in_options = False
 
         if not in_options:
-            raise ValueError( 
+            raise ValueError(
                 "'{name}' must be in {options!r} (got {value!r})".format(
                     name=attr.name, options=self.options, value=value
                 )
-            ) 
- 
-    def __repr__(self): 
+            )
+
+    def __repr__(self):
         return "<in_ validator with options {options!r}>".format(
             options=self.options
-        ) 
- 
- 
-def in_(options): 
-    """ 
+        )
+
+
+def in_(options):
+    """
     A validator that raises a `ValueError` if the initializer is called
-    with a value that does not belong in the options provided.  The check is 
-    performed using ``value in options``. 
- 
-    :param options: Allowed options. 
+    with a value that does not belong in the options provided.  The check is
+    performed using ``value in options``.
+
+    :param options: Allowed options.
     :type options: list, tuple, `enum.Enum`, ...
- 
-    :raises ValueError: With a human readable error message, the attribute (of 
+
+    :raises ValueError: With a human readable error message, the attribute (of
        type `attr.Attribute`), the expected options, and the value it
-       got. 
- 
-    .. versionadded:: 17.1.0 
-    """ 
-    return _InValidator(options) 
+       got.
+
+    .. versionadded:: 17.1.0
+    """
+    return _InValidator(options)
 
 
 @attrs(repr=False, slots=False, hash=True)
diff --git a/contrib/python/attrs/ya.make b/contrib/python/attrs/ya.make
index 397cb2e55e..15fb4c423b 100644
--- a/contrib/python/attrs/ya.make
+++ b/contrib/python/attrs/ya.make
@@ -1,37 +1,37 @@
 PY23_LIBRARY()
- 
+
 LICENSE(MIT)
 
-OWNER(g:python-contrib) 
- 
+OWNER(g:python-contrib)
+
 VERSION(21.2.0)
- 
-NO_LINT() 
- 
-PY_SRCS( 
-    TOP_LEVEL 
-    attr/__init__.py 
+
+NO_LINT()
+
+PY_SRCS(
+    TOP_LEVEL
+    attr/__init__.py
     attr/__init__.pyi
     attr/_cmp.py
     attr/_cmp.pyi
-    attr/_compat.py 
-    attr/_config.py 
-    attr/_funcs.py 
-    attr/_make.py 
+    attr/_compat.py
+    attr/_config.py
+    attr/_funcs.py
+    attr/_make.py
     attr/_version_info.py
     attr/_version_info.pyi
-    attr/converters.py 
+    attr/converters.py
     attr/converters.pyi
-    attr/exceptions.py 
+    attr/exceptions.py
     attr/exceptions.pyi
-    attr/filters.py 
+    attr/filters.py
     attr/filters.pyi
     attr/setters.py
     attr/setters.pyi
-    attr/validators.py 
+    attr/validators.py
     attr/validators.pyi
-) 
- 
+)
+
 IF (PYTHON3)
     PY_SRCS(
         TOP_LEVEL
@@ -46,4 +46,4 @@ RESOURCE_FILES(
     attr/py.typed
 )
 
-END() 
+END()