add ydb deps

1 files changed, 1736 insertions, 0 deletions

diff --git a/contrib/tools/python3/src/Lib/ast.py b/contrib/tools/python3/src/Lib/ast.py
new file mode 100644
index 0000000000..623b9a1b80
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/ast.py
@@ -0,0 +1,1736 @@
+"""
+    ast
+    ~~~
+
+    The `ast` module helps Python applications to process trees of the Python
+    abstract syntax grammar.  The abstract syntax itself might change with
+    each Python release; this module helps to find out programmatically what
+    the current grammar looks like and allows modifications of it.
+
+    An abstract syntax tree can be generated by passing `ast.PyCF_ONLY_AST` as
+    a flag to the `compile()` builtin function or by using the `parse()`
+    function from this module.  The result will be a tree of objects whose
+    classes all inherit from `ast.AST`.
+
+    A modified abstract syntax tree can be compiled into a Python code object
+    using the built-in `compile()` function.
+
+    Additionally various helper functions are provided that make working with
+    the trees simpler.  The main intention of the helper functions and this
+    module in general is to provide an easy to use interface for libraries
+    that work tightly with the python syntax (template engines for example).
+
+
+    :copyright: Copyright 2008 by Armin Ronacher.
+    :license: Python License.
+"""
+import sys
+from _ast import *
+from contextlib import contextmanager, nullcontext
+from enum import IntEnum, auto, _simple_enum
+
+
+def parse(source, filename='<unknown>', mode='exec', *,
+          type_comments=False, feature_version=None):
+    """
+    Parse the source into an AST node.
+    Equivalent to compile(source, filename, mode, PyCF_ONLY_AST).
+    Pass type_comments=True to get back type comments where the syntax allows.
+    """
+    flags = PyCF_ONLY_AST
+    if type_comments:
+        flags |= PyCF_TYPE_COMMENTS
+    if isinstance(feature_version, tuple):
+        major, minor = feature_version  # Should be a 2-tuple.
+        assert major == 3
+        feature_version = minor
+    elif feature_version is None:
+        feature_version = -1
+    # Else it should be an int giving the minor version for 3.x.
+    return compile(source, filename, mode, flags,
+                   _feature_version=feature_version)
+
+
+def literal_eval(node_or_string):
+    """
+    Evaluate an expression node or a string containing only a Python
+    expression.  The string or node provided may only consist of the following
+    Python literal structures: strings, bytes, numbers, tuples, lists, dicts,
+    sets, booleans, and None.
+
+    Caution: A complex expression can overflow the C stack and cause a crash.
+    """
+    if isinstance(node_or_string, str):
+        node_or_string = parse(node_or_string.lstrip(" \t"), mode='eval')
+    if isinstance(node_or_string, Expression):
+        node_or_string = node_or_string.body
+    def _raise_malformed_node(node):
+        msg = "malformed node or string"
+        if lno := getattr(node, 'lineno', None):
+            msg += f' on line {lno}'
+        raise ValueError(msg + f': {node!r}')
+    def _convert_num(node):
+        if not isinstance(node, Constant) or type(node.value) not in (int, float, complex):
+            _raise_malformed_node(node)
+        return node.value
+    def _convert_signed_num(node):
+        if isinstance(node, UnaryOp) and isinstance(node.op, (UAdd, USub)):
+            operand = _convert_num(node.operand)
+            if isinstance(node.op, UAdd):
+                return + operand
+            else:
+                return - operand
+        return _convert_num(node)
+    def _convert(node):
+        if isinstance(node, Constant):
+            return node.value
+        elif isinstance(node, Tuple):
+            return tuple(map(_convert, node.elts))
+        elif isinstance(node, List):
+            return list(map(_convert, node.elts))
+        elif isinstance(node, Set):
+            return set(map(_convert, node.elts))
+        elif (isinstance(node, Call) and isinstance(node.func, Name) and
+              node.func.id == 'set' and node.args == node.keywords == []):
+            return set()
+        elif isinstance(node, Dict):
+            if len(node.keys) != len(node.values):
+                _raise_malformed_node(node)
+            return dict(zip(map(_convert, node.keys),
+                            map(_convert, node.values)))
+        elif isinstance(node, BinOp) and isinstance(node.op, (Add, Sub)):
+            left = _convert_signed_num(node.left)
+            right = _convert_num(node.right)
+            if isinstance(left, (int, float)) and isinstance(right, complex):
+                if isinstance(node.op, Add):
+                    return left + right
+                else:
+                    return left - right
+        return _convert_signed_num(node)
+    return _convert(node_or_string)
+
+
+def dump(node, annotate_fields=True, include_attributes=False, *, indent=None):
+    """
+    Return a formatted dump of the tree in node.  This is mainly useful for
+    debugging purposes.  If annotate_fields is true (by default),
+    the returned string will show the names and the values for fields.
+    If annotate_fields is false, the result string will be more compact by
+    omitting unambiguous field names.  Attributes such as line
+    numbers and column offsets are not dumped by default.  If this is wanted,
+    include_attributes can be set to true.  If indent is a non-negative
+    integer or string, then the tree will be pretty-printed with that indent
+    level. None (the default) selects the single line representation.
+    """
+    def _format(node, level=0):
+        if indent is not None:
+            level += 1
+            prefix = '\n' + indent * level
+            sep = ',\n' + indent * level
+        else:
+            prefix = ''
+            sep = ', '
+        if isinstance(node, AST):
+            cls = type(node)
+            args = []
+            allsimple = True
+            keywords = annotate_fields
+            for name in node._fields:
+                try:
+                    value = getattr(node, name)
+                except AttributeError:
+                    keywords = True
+                    continue
+                if value is None and getattr(cls, name, ...) is None:
+                    keywords = True
+                    continue
+                value, simple = _format(value, level)
+                allsimple = allsimple and simple
+                if keywords:
+                    args.append('%s=%s' % (name, value))
+                else:
+                    args.append(value)
+            if include_attributes and node._attributes:
+                for name in node._attributes:
+                    try:
+                        value = getattr(node, name)
+                    except AttributeError:
+                        continue
+                    if value is None and getattr(cls, name, ...) is None:
+                        continue
+                    value, simple = _format(value, level)
+                    allsimple = allsimple and simple
+                    args.append('%s=%s' % (name, value))
+            if allsimple and len(args) <= 3:
+                return '%s(%s)' % (node.__class__.__name__, ', '.join(args)), not args
+            return '%s(%s%s)' % (node.__class__.__name__, prefix, sep.join(args)), False
+        elif isinstance(node, list):
+            if not node:
+                return '[]', True
+            return '[%s%s]' % (prefix, sep.join(_format(x, level)[0] for x in node)), False
+        return repr(node), True
+
+    if not isinstance(node, AST):
+        raise TypeError('expected AST, got %r' % node.__class__.__name__)
+    if indent is not None and not isinstance(indent, str):
+        indent = ' ' * indent
+    return _format(node)[0]
+
+
+def copy_location(new_node, old_node):
+    """
+    Copy source location (`lineno`, `col_offset`, `end_lineno`, and `end_col_offset`
+    attributes) from *old_node* to *new_node* if possible, and return *new_node*.
+    """
+    for attr in 'lineno', 'col_offset', 'end_lineno', 'end_col_offset':
+        if attr in old_node._attributes and attr in new_node._attributes:
+            value = getattr(old_node, attr, None)
+            # end_lineno and end_col_offset are optional attributes, and they
+            # should be copied whether the value is None or not.
+            if value is not None or (
+                hasattr(old_node, attr) and attr.startswith("end_")
+            ):
+                setattr(new_node, attr, value)
+    return new_node
+
+
+def fix_missing_locations(node):
+    """
+    When you compile a node tree with compile(), the compiler expects lineno and
+    col_offset attributes for every node that supports them.  This is rather
+    tedious to fill in for generated nodes, so this helper adds these attributes
+    recursively where not already set, by setting them to the values of the
+    parent node.  It works recursively starting at *node*.
+    """
+    def _fix(node, lineno, col_offset, end_lineno, end_col_offset):
+        if 'lineno' in node._attributes:
+            if not hasattr(node, 'lineno'):
+                node.lineno = lineno
+            else:
+                lineno = node.lineno
+        if 'end_lineno' in node._attributes:
+            if getattr(node, 'end_lineno', None) is None:
+                node.end_lineno = end_lineno
+            else:
+                end_lineno = node.end_lineno
+        if 'col_offset' in node._attributes:
+            if not hasattr(node, 'col_offset'):
+                node.col_offset = col_offset
+            else:
+                col_offset = node.col_offset
+        if 'end_col_offset' in node._attributes:
+            if getattr(node, 'end_col_offset', None) is None:
+                node.end_col_offset = end_col_offset
+            else:
+                end_col_offset = node.end_col_offset
+        for child in iter_child_nodes(node):
+            _fix(child, lineno, col_offset, end_lineno, end_col_offset)
+    _fix(node, 1, 0, 1, 0)
+    return node
+
+
+def increment_lineno(node, n=1):
+    """
+    Increment the line number and end line number of each node in the tree
+    starting at *node* by *n*. This is useful to "move code" to a different
+    location in a file.
+    """
+    for child in walk(node):
+        # TypeIgnore is a special case where lineno is not an attribute
+        # but rather a field of the node itself.
+        if isinstance(child, TypeIgnore):
+            child.lineno = getattr(child, 'lineno', 0) + n
+            continue
+
+        if 'lineno' in child._attributes:
+            child.lineno = getattr(child, 'lineno', 0) + n
+        if (
+            "end_lineno" in child._attributes
+            and (end_lineno := getattr(child, "end_lineno", 0)) is not None
+        ):
+            child.end_lineno = end_lineno + n
+    return node
+
+
+def iter_fields(node):
+    """
+    Yield a tuple of ``(fieldname, value)`` for each field in ``node._fields``
+    that is present on *node*.
+    """
+    for field in node._fields:
+        try:
+            yield field, getattr(node, field)
+        except AttributeError:
+            pass
+
+
+def iter_child_nodes(node):
+    """
+    Yield all direct child nodes of *node*, that is, all fields that are nodes
+    and all items of fields that are lists of nodes.
+    """
+    for name, field in iter_fields(node):
+        if isinstance(field, AST):
+            yield field
+        elif isinstance(field, list):
+            for item in field:
+                if isinstance(item, AST):
+                    yield item
+
+
+def get_docstring(node, clean=True):
+    """
+    Return the docstring for the given node or None if no docstring can
+    be found.  If the node provided does not have docstrings a TypeError
+    will be raised.
+
+    If *clean* is `True`, all tabs are expanded to spaces and any whitespace
+    that can be uniformly removed from the second line onwards is removed.
+    """
+    if not isinstance(node, (AsyncFunctionDef, FunctionDef, ClassDef, Module)):
+        raise TypeError("%r can't have docstrings" % node.__class__.__name__)
+    if not(node.body and isinstance(node.body[0], Expr)):
+        return None
+    node = node.body[0].value
+    if isinstance(node, Str):
+        text = node.s
+    elif isinstance(node, Constant) and isinstance(node.value, str):
+        text = node.value
+    else:
+        return None
+    if clean:
+        import inspect
+        text = inspect.cleandoc(text)
+    return text
+
+
+def _splitlines_no_ff(source):
+    """Split a string into lines ignoring form feed and other chars.
+
+    This mimics how the Python parser splits source code.
+    """
+    idx = 0
+    lines = []
+    next_line = ''
+    while idx < len(source):
+        c = source[idx]
+        next_line += c
+        idx += 1
+        # Keep \r\n together
+        if c == '\r' and idx < len(source) and source[idx] == '\n':
+            next_line += '\n'
+            idx += 1
+        if c in '\r\n':
+            lines.append(next_line)
+            next_line = ''
+
+    if next_line:
+        lines.append(next_line)
+    return lines
+
+
+def _pad_whitespace(source):
+    r"""Replace all chars except '\f\t' in a line with spaces."""
+    result = ''
+    for c in source:
+        if c in '\f\t':
+            result += c
+        else:
+            result += ' '
+    return result
+
+
+def get_source_segment(source, node, *, padded=False):
+    """Get source code segment of the *source* that generated *node*.
+
+    If some location information (`lineno`, `end_lineno`, `col_offset`,
+    or `end_col_offset`) is missing, return None.
+
+    If *padded* is `True`, the first line of a multi-line statement will
+    be padded with spaces to match its original position.
+    """
+    try:
+        if node.end_lineno is None or node.end_col_offset is None:
+            return None
+        lineno = node.lineno - 1
+        end_lineno = node.end_lineno - 1
+        col_offset = node.col_offset
+        end_col_offset = node.end_col_offset
+    except AttributeError:
+        return None
+
+    lines = _splitlines_no_ff(source)
+    if end_lineno == lineno:
+        return lines[lineno].encode()[col_offset:end_col_offset].decode()
+
+    if padded:
+        padding = _pad_whitespace(lines[lineno].encode()[:col_offset].decode())
+    else:
+        padding = ''
+
+    first = padding + lines[lineno].encode()[col_offset:].decode()
+    last = lines[end_lineno].encode()[:end_col_offset].decode()
+    lines = lines[lineno+1:end_lineno]
+
+    lines.insert(0, first)
+    lines.append(last)
+    return ''.join(lines)
+
+
+def walk(node):
+    """
+    Recursively yield all descendant nodes in the tree starting at *node*
+    (including *node* itself), in no specified order.  This is useful if you
+    only want to modify nodes in place and don't care about the context.
+    """
+    from collections import deque
+    todo = deque([node])
+    while todo:
+        node = todo.popleft()
+        todo.extend(iter_child_nodes(node))
+        yield node
+
+
+class NodeVisitor(object):
+    """
+    A node visitor base class that walks the abstract syntax tree and calls a
+    visitor function for every node found.  This function may return a value
+    which is forwarded by the `visit` method.
+
+    This class is meant to be subclassed, with the subclass adding visitor
+    methods.
+
+    Per default the visitor functions for the nodes are ``'visit_'`` +
+    class name of the node.  So a `TryFinally` node visit function would
+    be `visit_TryFinally`.  This behavior can be changed by overriding
+    the `visit` method.  If no visitor function exists for a node
+    (return value `None`) the `generic_visit` visitor is used instead.
+
+    Don't use the `NodeVisitor` if you want to apply changes to nodes during
+    traversing.  For this a special visitor exists (`NodeTransformer`) that
+    allows modifications.
+    """
+
+    def visit(self, node):
+        """Visit a node."""
+        method = 'visit_' + node.__class__.__name__
+        visitor = getattr(self, method, self.generic_visit)
+        return visitor(node)
+
+    def generic_visit(self, node):
+        """Called if no explicit visitor function exists for a node."""
+        for field, value in iter_fields(node):
+            if isinstance(value, list):
+                for item in value:
+                    if isinstance(item, AST):
+                        self.visit(item)
+            elif isinstance(value, AST):
+                self.visit(value)
+
+    def visit_Constant(self, node):
+        value = node.value
+        type_name = _const_node_type_names.get(type(value))
+        if type_name is None:
+            for cls, name in _const_node_type_names.items():
+                if isinstance(value, cls):
+                    type_name = name
+                    break
+        if type_name is not None:
+            method = 'visit_' + type_name
+            try:
+                visitor = getattr(self, method)
+            except AttributeError:
+                pass
+            else:
+                import warnings
+                warnings.warn(f"{method} is deprecated; add visit_Constant",
+                              DeprecationWarning, 2)
+                return visitor(node)
+        return self.generic_visit(node)
+
+
+class NodeTransformer(NodeVisitor):
+    """
+    A :class:`NodeVisitor` subclass that walks the abstract syntax tree and
+    allows modification of nodes.
+
+    The `NodeTransformer` will walk the AST and use the return value of the
+    visitor methods to replace or remove the old node.  If the return value of
+    the visitor method is ``None``, the node will be removed from its location,
+    otherwise it is replaced with the return value.  The return value may be the
+    original node in which case no replacement takes place.
+
+    Here is an example transformer that rewrites all occurrences of name lookups
+    (``foo``) to ``data['foo']``::
+
+       class RewriteName(NodeTransformer):
+
+           def visit_Name(self, node):
+               return Subscript(
+                   value=Name(id='data', ctx=Load()),
+                   slice=Constant(value=node.id),
+                   ctx=node.ctx
+               )
+
+    Keep in mind that if the node you're operating on has child nodes you must
+    either transform the child nodes yourself or call the :meth:`generic_visit`
+    method for the node first.
+
+    For nodes that were part of a collection of statements (that applies to all
+    statement nodes), the visitor may also return a list of nodes rather than
+    just a single node.
+
+    Usually you use the transformer like this::
+
+       node = YourTransformer().visit(node)
+    """
+
+    def generic_visit(self, node):
+        for field, old_value in iter_fields(node):
+            if isinstance(old_value, list):
+                new_values = []
+                for value in old_value:
+                    if isinstance(value, AST):
+                        value = self.visit(value)
+                        if value is None:
+                            continue
+                        elif not isinstance(value, AST):
+                            new_values.extend(value)
+                            continue
+                    new_values.append(value)
+                old_value[:] = new_values
+            elif isinstance(old_value, AST):
+                new_node = self.visit(old_value)
+                if new_node is None:
+                    delattr(node, field)
+                else:
+                    setattr(node, field, new_node)
+        return node
+
+
+# If the ast module is loaded more than once, only add deprecated methods once
+if not hasattr(Constant, 'n'):
+    # The following code is for backward compatibility.
+    # It will be removed in future.
+
+    def _getter(self):
+        """Deprecated. Use value instead."""
+        return self.value
+
+    def _setter(self, value):
+        self.value = value
+
+    Constant.n = property(_getter, _setter)
+    Constant.s = property(_getter, _setter)
+
+class _ABC(type):
+
+    def __init__(cls, *args):
+        cls.__doc__ = """Deprecated AST node class. Use ast.Constant instead"""
+
+    def __instancecheck__(cls, inst):
+        if not isinstance(inst, Constant):
+            return False
+        if cls in _const_types:
+            try:
+                value = inst.value
+            except AttributeError:
+                return False
+            else:
+                return (
+                    isinstance(value, _const_types[cls]) and
+                    not isinstance(value, _const_types_not.get(cls, ()))
+                )
+        return type.__instancecheck__(cls, inst)
+
+def _new(cls, *args, **kwargs):
+    for key in kwargs:
+        if key not in cls._fields:
+            # arbitrary keyword arguments are accepted
+            continue
+        pos = cls._fields.index(key)
+        if pos < len(args):
+            raise TypeError(f"{cls.__name__} got multiple values for argument {key!r}")
+    if cls in _const_types:
+        return Constant(*args, **kwargs)
+    return Constant.__new__(cls, *args, **kwargs)
+
+class Num(Constant, metaclass=_ABC):
+    _fields = ('n',)
+    __new__ = _new
+
+class Str(Constant, metaclass=_ABC):
+    _fields = ('s',)
+    __new__ = _new
+
+class Bytes(Constant, metaclass=_ABC):
+    _fields = ('s',)
+    __new__ = _new
+
+class NameConstant(Constant, metaclass=_ABC):
+    __new__ = _new
+
+class Ellipsis(Constant, metaclass=_ABC):
+    _fields = ()
+
+    def __new__(cls, *args, **kwargs):
+        if cls is Ellipsis:
+            return Constant(..., *args, **kwargs)
+        return Constant.__new__(cls, *args, **kwargs)
+
+_const_types = {
+    Num: (int, float, complex),
+    Str: (str,),
+    Bytes: (bytes,),
+    NameConstant: (type(None), bool),
+    Ellipsis: (type(...),),
+}
+_const_types_not = {
+    Num: (bool,),
+}
+
+_const_node_type_names = {
+    bool: 'NameConstant',  # should be before int
+    type(None): 'NameConstant',
+    int: 'Num',
+    float: 'Num',
+    complex: 'Num',
+    str: 'Str',
+    bytes: 'Bytes',
+    type(...): 'Ellipsis',
+}
+
+class slice(AST):
+    """Deprecated AST node class."""
+
+class Index(slice):
+    """Deprecated AST node class. Use the index value directly instead."""
+    def __new__(cls, value, **kwargs):
+        return value
+
+class ExtSlice(slice):
+    """Deprecated AST node class. Use ast.Tuple instead."""
+    def __new__(cls, dims=(), **kwargs):
+        return Tuple(list(dims), Load(), **kwargs)
+
+# If the ast module is loaded more than once, only add deprecated methods once
+if not hasattr(Tuple, 'dims'):
+    # The following code is for backward compatibility.
+    # It will be removed in future.
+
+    def _dims_getter(self):
+        """Deprecated. Use elts instead."""
+        return self.elts
+
+    def _dims_setter(self, value):
+        self.elts = value
+
+    Tuple.dims = property(_dims_getter, _dims_setter)
+
+class Suite(mod):
+    """Deprecated AST node class.  Unused in Python 3."""
+
+class AugLoad(expr_context):
+    """Deprecated AST node class.  Unused in Python 3."""
+
+class AugStore(expr_context):
+    """Deprecated AST node class.  Unused in Python 3."""
+
+class Param(expr_context):
+    """Deprecated AST node class.  Unused in Python 3."""
+
+
+# Large float and imaginary literals get turned into infinities in the AST.
+# We unparse those infinities to INFSTR.
+_INFSTR = "1e" + repr(sys.float_info.max_10_exp + 1)
+
+@_simple_enum(IntEnum)
+class _Precedence:
+    """Precedence table that originated from python grammar."""
+
+    NAMED_EXPR = auto()      # <target> := <expr1>
+    TUPLE = auto()           # <expr1>, <expr2>
+    YIELD = auto()           # 'yield', 'yield from'
+    TEST = auto()            # 'if'-'else', 'lambda'
+    OR = auto()              # 'or'
+    AND = auto()             # 'and'
+    NOT = auto()             # 'not'
+    CMP = auto()             # '<', '>', '==', '>=', '<=', '!=',
+                             # 'in', 'not in', 'is', 'is not'
+    EXPR = auto()
+    BOR = EXPR               # '|'
+    BXOR = auto()            # '^'
+    BAND = auto()            # '&'
+    SHIFT = auto()           # '<<', '>>'
+    ARITH = auto()           # '+', '-'
+    TERM = auto()            # '*', '@', '/', '%', '//'
+    FACTOR = auto()          # unary '+', '-', '~'
+    POWER = auto()           # '**'
+    AWAIT = auto()           # 'await'
+    ATOM = auto()
+
+    def next(self):
+        try:
+            return self.__class__(self + 1)
+        except ValueError:
+            return self
+
+
+_SINGLE_QUOTES = ("'", '"')
+_MULTI_QUOTES = ('"""', "'''")
+_ALL_QUOTES = (*_SINGLE_QUOTES, *_MULTI_QUOTES)
+
+class _Unparser(NodeVisitor):
+    """Methods in this class recursively traverse an AST and
+    output source code for the abstract syntax; original formatting
+    is disregarded."""
+
+    def __init__(self, *, _avoid_backslashes=False):
+        self._source = []
+        self._precedences = {}
+        self._type_ignores = {}
+        self._indent = 0
+        self._avoid_backslashes = _avoid_backslashes
+        self._in_try_star = False
+
+    def interleave(self, inter, f, seq):
+        """Call f on each item in seq, calling inter() in between."""
+        seq = iter(seq)
+        try:
+            f(next(seq))
+        except StopIteration:
+            pass
+        else:
+            for x in seq:
+                inter()
+                f(x)
+
+    def items_view(self, traverser, items):
+        """Traverse and separate the given *items* with a comma and append it to
+        the buffer. If *items* is a single item sequence, a trailing comma
+        will be added."""
+        if len(items) == 1:
+            traverser(items[0])
+            self.write(",")
+        else:
+            self.interleave(lambda: self.write(", "), traverser, items)
+
+    def maybe_newline(self):
+        """Adds a newline if it isn't the start of generated source"""
+        if self._source:
+            self.write("\n")
+
+    def fill(self, text=""):
+        """Indent a piece of text and append it, according to the current
+        indentation level"""
+        self.maybe_newline()
+        self.write("    " * self._indent + text)
+
+    def write(self, *text):
+        """Add new source parts"""
+        self._source.extend(text)
+
+    @contextmanager
+    def buffered(self, buffer = None):
+        if buffer is None:
+            buffer = []
+
+        original_source = self._source
+        self._source = buffer
+        yield buffer
+        self._source = original_source
+
+    @contextmanager
+    def block(self, *, extra = None):
+        """A context manager for preparing the source for blocks. It adds
+        the character':', increases the indentation on enter and decreases
+        the indentation on exit. If *extra* is given, it will be directly
+        appended after the colon character.
+        """
+        self.write(":")
+        if extra:
+            self.write(extra)
+        self._indent += 1
+        yield
+        self._indent -= 1
+
+    @contextmanager
+    def delimit(self, start, end):
+        """A context manager for preparing the source for expressions. It adds
+        *start* to the buffer and enters, after exit it adds *end*."""
+
+        self.write(start)
+        yield
+        self.write(end)
+
+    def delimit_if(self, start, end, condition):
+        if condition:
+            return self.delimit(start, end)
+        else:
+            return nullcontext()
+
+    def require_parens(self, precedence, node):
+        """Shortcut to adding precedence related parens"""
+        return self.delimit_if("(", ")", self.get_precedence(node) > precedence)
+
+    def get_precedence(self, node):
+        return self._precedences.get(node, _Precedence.TEST)
+
+    def set_precedence(self, precedence, *nodes):
+        for node in nodes:
+            self._precedences[node] = precedence
+
+    def get_raw_docstring(self, node):
+        """If a docstring node is found in the body of the *node* parameter,
+        return that docstring node, None otherwise.
+
+        Logic mirrored from ``_PyAST_GetDocString``."""
+        if not isinstance(
+            node, (AsyncFunctionDef, FunctionDef, ClassDef, Module)
+        ) or len(node.body) < 1:
+            return None
+        node = node.body[0]
+        if not isinstance(node, Expr):
+            return None
+        node = node.value
+        if isinstance(node, Constant) and isinstance(node.value, str):
+            return node
+
+    def get_type_comment(self, node):
+        comment = self._type_ignores.get(node.lineno) or node.type_comment
+        if comment is not None:
+            return f" # type: {comment}"
+
+    def traverse(self, node):
+        if isinstance(node, list):
+            for item in node:
+                self.traverse(item)
+        else:
+            super().visit(node)
+
+    # Note: as visit() resets the output text, do NOT rely on
+    # NodeVisitor.generic_visit to handle any nodes (as it calls back in to
+    # the subclass visit() method, which resets self._source to an empty list)
+    def visit(self, node):
+        """Outputs a source code string that, if converted back to an ast
+        (using ast.parse) will generate an AST equivalent to *node*"""
+        self._source = []
+        self.traverse(node)
+        return "".join(self._source)
+
+    def _write_docstring_and_traverse_body(self, node):
+        if (docstring := self.get_raw_docstring(node)):
+            self._write_docstring(docstring)
+            self.traverse(node.body[1:])
+        else:
+            self.traverse(node.body)
+
+    def visit_Module(self, node):
+        self._type_ignores = {
+            ignore.lineno: f"ignore{ignore.tag}"
+            for ignore in node.type_ignores
+        }
+        self._write_docstring_and_traverse_body(node)
+        self._type_ignores.clear()
+
+    def visit_FunctionType(self, node):
+        with self.delimit("(", ")"):
+            self.interleave(
+                lambda: self.write(", "), self.traverse, node.argtypes
+            )
+
+        self.write(" -> ")
+        self.traverse(node.returns)
+
+    def visit_Expr(self, node):
+        self.fill()
+        self.set_precedence(_Precedence.YIELD, node.value)
+        self.traverse(node.value)
+
+    def visit_NamedExpr(self, node):
+        with self.require_parens(_Precedence.NAMED_EXPR, node):
+            self.set_precedence(_Precedence.ATOM, node.target, node.value)
+            self.traverse(node.target)
+            self.write(" := ")
+            self.traverse(node.value)
+
+    def visit_Import(self, node):
+        self.fill("import ")
+        self.interleave(lambda: self.write(", "), self.traverse, node.names)
+
+    def visit_ImportFrom(self, node):
+        self.fill("from ")
+        self.write("." * (node.level or 0))
+        if node.module:
+            self.write(node.module)
+        self.write(" import ")
+        self.interleave(lambda: self.write(", "), self.traverse, node.names)
+
+    def visit_Assign(self, node):
+        self.fill()
+        for target in node.targets:
+            self.set_precedence(_Precedence.TUPLE, target)
+            self.traverse(target)
+            self.write(" = ")
+        self.traverse(node.value)
+        if type_comment := self.get_type_comment(node):
+            self.write(type_comment)
+
+    def visit_AugAssign(self, node):
+        self.fill()
+        self.traverse(node.target)
+        self.write(" " + self.binop[node.op.__class__.__name__] + "= ")
+        self.traverse(node.value)
+
+    def visit_AnnAssign(self, node):
+        self.fill()
+        with self.delimit_if("(", ")", not node.simple and isinstance(node.target, Name)):
+            self.traverse(node.target)
+        self.write(": ")
+        self.traverse(node.annotation)
+        if node.value:
+            self.write(" = ")
+            self.traverse(node.value)
+
+    def visit_Return(self, node):
+        self.fill("return")
+        if node.value:
+            self.write(" ")
+            self.traverse(node.value)
+
+    def visit_Pass(self, node):
+        self.fill("pass")
+
+    def visit_Break(self, node):
+        self.fill("break")
+
+    def visit_Continue(self, node):
+        self.fill("continue")
+
+    def visit_Delete(self, node):
+        self.fill("del ")
+        self.interleave(lambda: self.write(", "), self.traverse, node.targets)
+
+    def visit_Assert(self, node):
+        self.fill("assert ")
+        self.traverse(node.test)
+        if node.msg:
+            self.write(", ")
+            self.traverse(node.msg)
+
+    def visit_Global(self, node):
+        self.fill("global ")
+        self.interleave(lambda: self.write(", "), self.write, node.names)
+
+    def visit_Nonlocal(self, node):
+        self.fill("nonlocal ")
+        self.interleave(lambda: self.write(", "), self.write, node.names)
+
+    def visit_Await(self, node):
+        with self.require_parens(_Precedence.AWAIT, node):
+            self.write("await")
+            if node.value:
+                self.write(" ")
+                self.set_precedence(_Precedence.ATOM, node.value)
+                self.traverse(node.value)
+
+    def visit_Yield(self, node):
+        with self.require_parens(_Precedence.YIELD, node):
+            self.write("yield")
+            if node.value:
+                self.write(" ")
+                self.set_precedence(_Precedence.ATOM, node.value)
+                self.traverse(node.value)
+
+    def visit_YieldFrom(self, node):
+        with self.require_parens(_Precedence.YIELD, node):
+            self.write("yield from ")
+            if not node.value:
+                raise ValueError("Node can't be used without a value attribute.")
+            self.set_precedence(_Precedence.ATOM, node.value)
+            self.traverse(node.value)
+
+    def visit_Raise(self, node):
+        self.fill("raise")
+        if not node.exc:
+            if node.cause:
+                raise ValueError(f"Node can't use cause without an exception.")
+            return
+        self.write(" ")
+        self.traverse(node.exc)
+        if node.cause:
+            self.write(" from ")
+            self.traverse(node.cause)
+
+    def do_visit_try(self, node):
+        self.fill("try")
+        with self.block():
+            self.traverse(node.body)
+        for ex in node.handlers:
+            self.traverse(ex)
+        if node.orelse:
+            self.fill("else")
+            with self.block():
+                self.traverse(node.orelse)
+        if node.finalbody:
+            self.fill("finally")
+            with self.block():
+                self.traverse(node.finalbody)
+
+    def visit_Try(self, node):
+        prev_in_try_star = self._in_try_star
+        try:
+            self._in_try_star = False
+            self.do_visit_try(node)
+        finally:
+            self._in_try_star = prev_in_try_star
+
+    def visit_TryStar(self, node):
+        prev_in_try_star = self._in_try_star
+        try:
+            self._in_try_star = True
+            self.do_visit_try(node)
+        finally:
+            self._in_try_star = prev_in_try_star
+
+    def visit_ExceptHandler(self, node):
+        self.fill("except*" if self._in_try_star else "except")
+        if node.type:
+            self.write(" ")
+            self.traverse(node.type)
+        if node.name:
+            self.write(" as ")
+            self.write(node.name)
+        with self.block():
+            self.traverse(node.body)
+
+    def visit_ClassDef(self, node):
+        self.maybe_newline()
+        for deco in node.decorator_list:
+            self.fill("@")
+            self.traverse(deco)
+        self.fill("class " + node.name)
+        with self.delimit_if("(", ")", condition = node.bases or node.keywords):
+            comma = False
+            for e in node.bases:
+                if comma:
+                    self.write(", ")
+                else:
+                    comma = True
+                self.traverse(e)
+            for e in node.keywords:
+                if comma:
+                    self.write(", ")
+                else:
+                    comma = True
+                self.traverse(e)
+
+        with self.block():
+            self._write_docstring_and_traverse_body(node)
+
+    def visit_FunctionDef(self, node):
+        self._function_helper(node, "def")
+
+    def visit_AsyncFunctionDef(self, node):
+        self._function_helper(node, "async def")
+
+    def _function_helper(self, node, fill_suffix):
+        self.maybe_newline()
+        for deco in node.decorator_list:
+            self.fill("@")
+            self.traverse(deco)
+        def_str = fill_suffix + " " + node.name
+        self.fill(def_str)
+        with self.delimit("(", ")"):
+            self.traverse(node.args)
+        if node.returns:
+            self.write(" -> ")
+            self.traverse(node.returns)
+        with self.block(extra=self.get_type_comment(node)):
+            self._write_docstring_and_traverse_body(node)
+
+    def visit_For(self, node):
+        self._for_helper("for ", node)
+
+    def visit_AsyncFor(self, node):
+        self._for_helper("async for ", node)
+
+    def _for_helper(self, fill, node):
+        self.fill(fill)
+        self.set_precedence(_Precedence.TUPLE, node.target)
+        self.traverse(node.target)
+        self.write(" in ")
+        self.traverse(node.iter)
+        with self.block(extra=self.get_type_comment(node)):
+            self.traverse(node.body)
+        if node.orelse:
+            self.fill("else")
+            with self.block():
+                self.traverse(node.orelse)
+
+    def visit_If(self, node):
+        self.fill("if ")
+        self.traverse(node.test)
+        with self.block():
+            self.traverse(node.body)
+        # collapse nested ifs into equivalent elifs.
+        while node.orelse and len(node.orelse) == 1 and isinstance(node.orelse[0], If):
+            node = node.orelse[0]
+            self.fill("elif ")
+            self.traverse(node.test)
+            with self.block():
+                self.traverse(node.body)
+        # final else
+        if node.orelse:
+            self.fill("else")
+            with self.block():
+                self.traverse(node.orelse)
+
+    def visit_While(self, node):
+        self.fill("while ")
+        self.traverse(node.test)
+        with self.block():
+            self.traverse(node.body)
+        if node.orelse:
+            self.fill("else")
+            with self.block():
+                self.traverse(node.orelse)
+
+    def visit_With(self, node):
+        self.fill("with ")
+        self.interleave(lambda: self.write(", "), self.traverse, node.items)
+        with self.block(extra=self.get_type_comment(node)):
+            self.traverse(node.body)
+
+    def visit_AsyncWith(self, node):
+        self.fill("async with ")
+        self.interleave(lambda: self.write(", "), self.traverse, node.items)
+        with self.block(extra=self.get_type_comment(node)):
+            self.traverse(node.body)
+
+    def _str_literal_helper(
+        self, string, *, quote_types=_ALL_QUOTES, escape_special_whitespace=False
+    ):
+        """Helper for writing string literals, minimizing escapes.
+        Returns the tuple (string literal to write, possible quote types).
+        """
+        def escape_char(c):
+            # \n and \t are non-printable, but we only escape them if
+            # escape_special_whitespace is True
+            if not escape_special_whitespace and c in "\n\t":
+                return c
+            # Always escape backslashes and other non-printable characters
+            if c == "\\" or not c.isprintable():
+                return c.encode("unicode_escape").decode("ascii")
+            return c
+
+        escaped_string = "".join(map(escape_char, string))
+        possible_quotes = quote_types
+        if "\n" in escaped_string:
+            possible_quotes = [q for q in possible_quotes if q in _MULTI_QUOTES]
+        possible_quotes = [q for q in possible_quotes if q not in escaped_string]
+        if not possible_quotes:
+            # If there aren't any possible_quotes, fallback to using repr
+            # on the original string. Try to use a quote from quote_types,
+            # e.g., so that we use triple quotes for docstrings.
+            string = repr(string)
+            quote = next((q for q in quote_types if string[0] in q), string[0])
+            return string[1:-1], [quote]
+        if escaped_string:
+            # Sort so that we prefer '''"''' over """\""""
+            possible_quotes.sort(key=lambda q: q[0] == escaped_string[-1])
+            # If we're using triple quotes and we'd need to escape a final
+            # quote, escape it
+            if possible_quotes[0][0] == escaped_string[-1]:
+                assert len(possible_quotes[0]) == 3
+                escaped_string = escaped_string[:-1] + "\\" + escaped_string[-1]
+        return escaped_string, possible_quotes
+
+    def _write_str_avoiding_backslashes(self, string, *, quote_types=_ALL_QUOTES):
+        """Write string literal value with a best effort attempt to avoid backslashes."""
+        string, quote_types = self._str_literal_helper(string, quote_types=quote_types)
+        quote_type = quote_types[0]
+        self.write(f"{quote_type}{string}{quote_type}")
+
+    def visit_JoinedStr(self, node):
+        self.write("f")
+        if self._avoid_backslashes:
+            with self.buffered() as buffer:
+                self._write_fstring_inner(node)
+            return self._write_str_avoiding_backslashes("".join(buffer))
+
+        # If we don't need to avoid backslashes globally (i.e., we only need
+        # to avoid them inside FormattedValues), it's cosmetically preferred
+        # to use escaped whitespace. That is, it's preferred to use backslashes
+        # for cases like: f"{x}\n". To accomplish this, we keep track of what
+        # in our buffer corresponds to FormattedValues and what corresponds to
+        # Constant parts of the f-string, and allow escapes accordingly.
+        fstring_parts = []
+        for value in node.values:
+            with self.buffered() as buffer:
+                self._write_fstring_inner(value)
+            fstring_parts.append(
+                ("".join(buffer), isinstance(value, Constant))
+            )
+
+        new_fstring_parts = []
+        quote_types = list(_ALL_QUOTES)
+        for value, is_constant in fstring_parts:
+            value, quote_types = self._str_literal_helper(
+                value,
+                quote_types=quote_types,
+                escape_special_whitespace=is_constant,
+            )
+            new_fstring_parts.append(value)
+
+        value = "".join(new_fstring_parts)
+        quote_type = quote_types[0]
+        self.write(f"{quote_type}{value}{quote_type}")
+
+    def _write_fstring_inner(self, node):
+        if isinstance(node, JoinedStr):
+            # for both the f-string itself, and format_spec
+            for value in node.values:
+                self._write_fstring_inner(value)
+        elif isinstance(node, Constant) and isinstance(node.value, str):
+            value = node.value.replace("{", "{{").replace("}", "}}")
+            self.write(value)
+        elif isinstance(node, FormattedValue):
+            self.visit_FormattedValue(node)
+        else:
+            raise ValueError(f"Unexpected node inside JoinedStr, {node!r}")
+
+    def visit_FormattedValue(self, node):
+        def unparse_inner(inner):
+            unparser = type(self)(_avoid_backslashes=True)
+            unparser.set_precedence(_Precedence.TEST.next(), inner)
+            return unparser.visit(inner)
+
+        with self.delimit("{", "}"):
+            expr = unparse_inner(node.value)
+            if "\\" in expr:
+                raise ValueError(
+                    "Unable to avoid backslash in f-string expression part"
+                )
+            if expr.startswith("{"):
+                # Separate pair of opening brackets as "{ {"
+                self.write(" ")
+            self.write(expr)
+            if node.conversion != -1:
+                self.write(f"!{chr(node.conversion)}")
+            if node.format_spec:
+                self.write(":")
+                self._write_fstring_inner(node.format_spec)
+
+    def visit_Name(self, node):
+        self.write(node.id)
+
+    def _write_docstring(self, node):
+        self.fill()
+        if node.kind == "u":
+            self.write("u")
+        self._write_str_avoiding_backslashes(node.value, quote_types=_MULTI_QUOTES)
+
+    def _write_constant(self, value):
+        if isinstance(value, (float, complex)):
+            # Substitute overflowing decimal literal for AST infinities,
+            # and inf - inf for NaNs.
+            self.write(
+                repr(value)
+                .replace("inf", _INFSTR)
+                .replace("nan", f"({_INFSTR}-{_INFSTR})")
+            )
+        elif self._avoid_backslashes and isinstance(value, str):
+            self._write_str_avoiding_backslashes(value)
+        else:
+            self.write(repr(value))
+
+    def visit_Constant(self, node):
+        value = node.value
+        if isinstance(value, tuple):
+            with self.delimit("(", ")"):
+                self.items_view(self._write_constant, value)
+        elif value is ...:
+            self.write("...")
+        else:
+            if node.kind == "u":
+                self.write("u")
+            self._write_constant(node.value)
+
+    def visit_List(self, node):
+        with self.delimit("[", "]"):
+            self.interleave(lambda: self.write(", "), self.traverse, node.elts)
+
+    def visit_ListComp(self, node):
+        with self.delimit("[", "]"):
+            self.traverse(node.elt)
+            for gen in node.generators:
+                self.traverse(gen)
+
+    def visit_GeneratorExp(self, node):
+        with self.delimit("(", ")"):
+            self.traverse(node.elt)
+            for gen in node.generators:
+                self.traverse(gen)
+
+    def visit_SetComp(self, node):
+        with self.delimit("{", "}"):
+            self.traverse(node.elt)
+            for gen in node.generators:
+                self.traverse(gen)
+
+    def visit_DictComp(self, node):
+        with self.delimit("{", "}"):
+            self.traverse(node.key)
+            self.write(": ")
+            self.traverse(node.value)
+            for gen in node.generators:
+                self.traverse(gen)
+
+    def visit_comprehension(self, node):
+        if node.is_async:
+            self.write(" async for ")
+        else:
+            self.write(" for ")
+        self.set_precedence(_Precedence.TUPLE, node.target)
+        self.traverse(node.target)
+        self.write(" in ")
+        self.set_precedence(_Precedence.TEST.next(), node.iter, *node.ifs)
+        self.traverse(node.iter)
+        for if_clause in node.ifs:
+            self.write(" if ")
+            self.traverse(if_clause)
+
+    def visit_IfExp(self, node):
+        with self.require_parens(_Precedence.TEST, node):
+            self.set_precedence(_Precedence.TEST.next(), node.body, node.test)
+            self.traverse(node.body)
+            self.write(" if ")
+            self.traverse(node.test)
+            self.write(" else ")
+            self.set_precedence(_Precedence.TEST, node.orelse)
+            self.traverse(node.orelse)
+
+    def visit_Set(self, node):
+        if node.elts:
+            with self.delimit("{", "}"):
+                self.interleave(lambda: self.write(", "), self.traverse, node.elts)
+        else:
+            # `{}` would be interpreted as a dictionary literal, and
+            # `set` might be shadowed. Thus:
+            self.write('{*()}')
+
+    def visit_Dict(self, node):
+        def write_key_value_pair(k, v):
+            self.traverse(k)
+            self.write(": ")
+            self.traverse(v)
+
+        def write_item(item):
+            k, v = item
+            if k is None:
+                # for dictionary unpacking operator in dicts {**{'y': 2}}
+                # see PEP 448 for details
+                self.write("**")
+                self.set_precedence(_Precedence.EXPR, v)
+                self.traverse(v)
+            else:
+                write_key_value_pair(k, v)
+
+        with self.delimit("{", "}"):
+            self.interleave(
+                lambda: self.write(", "), write_item, zip(node.keys, node.values)
+            )
+
+    def visit_Tuple(self, node):
+        with self.delimit_if(
+            "(",
+            ")",
+            len(node.elts) == 0 or self.get_precedence(node) > _Precedence.TUPLE
+        ):
+            self.items_view(self.traverse, node.elts)
+
+    unop = {"Invert": "~", "Not": "not", "UAdd": "+", "USub": "-"}
+    unop_precedence = {
+        "not": _Precedence.NOT,
+        "~": _Precedence.FACTOR,
+        "+": _Precedence.FACTOR,
+        "-": _Precedence.FACTOR,
+    }
+
+    def visit_UnaryOp(self, node):
+        operator = self.unop[node.op.__class__.__name__]
+        operator_precedence = self.unop_precedence[operator]
+        with self.require_parens(operator_precedence, node):
+            self.write(operator)
+            # factor prefixes (+, -, ~) shouldn't be separated
+            # from the value they belong, (e.g: +1 instead of + 1)
+            if operator_precedence is not _Precedence.FACTOR:
+                self.write(" ")
+            self.set_precedence(operator_precedence, node.operand)
+            self.traverse(node.operand)
+
+    binop = {
+        "Add": "+",
+        "Sub": "-",
+        "Mult": "*",
+        "MatMult": "@",
+        "Div": "/",
+        "Mod": "%",
+        "LShift": "<<",
+        "RShift": ">>",
+        "BitOr": "|",
+        "BitXor": "^",
+        "BitAnd": "&",
+        "FloorDiv": "//",
+        "Pow": "**",
+    }
+
+    binop_precedence = {
+        "+": _Precedence.ARITH,
+        "-": _Precedence.ARITH,
+        "*": _Precedence.TERM,
+        "@": _Precedence.TERM,
+        "/": _Precedence.TERM,
+        "%": _Precedence.TERM,
+        "<<": _Precedence.SHIFT,
+        ">>": _Precedence.SHIFT,
+        "|": _Precedence.BOR,
+        "^": _Precedence.BXOR,
+        "&": _Precedence.BAND,
+        "//": _Precedence.TERM,
+        "**": _Precedence.POWER,
+    }
+
+    binop_rassoc = frozenset(("**",))
+    def visit_BinOp(self, node):
+        operator = self.binop[node.op.__class__.__name__]
+        operator_precedence = self.binop_precedence[operator]
+        with self.require_parens(operator_precedence, node):
+            if operator in self.binop_rassoc:
+                left_precedence = operator_precedence.next()
+                right_precedence = operator_precedence
+            else:
+                left_precedence = operator_precedence
+                right_precedence = operator_precedence.next()
+
+            self.set_precedence(left_precedence, node.left)
+            self.traverse(node.left)
+            self.write(f" {operator} ")
+            self.set_precedence(right_precedence, node.right)
+            self.traverse(node.right)
+
+    cmpops = {
+        "Eq": "==",
+        "NotEq": "!=",
+        "Lt": "<",
+        "LtE": "<=",
+        "Gt": ">",
+        "GtE": ">=",
+        "Is": "is",
+        "IsNot": "is not",
+        "In": "in",
+        "NotIn": "not in",
+    }
+
+    def visit_Compare(self, node):
+        with self.require_parens(_Precedence.CMP, node):
+            self.set_precedence(_Precedence.CMP.next(), node.left, *node.comparators)
+            self.traverse(node.left)
+            for o, e in zip(node.ops, node.comparators):
+                self.write(" " + self.cmpops[o.__class__.__name__] + " ")
+                self.traverse(e)
+
+    boolops = {"And": "and", "Or": "or"}
+    boolop_precedence = {"and": _Precedence.AND, "or": _Precedence.OR}
+
+    def visit_BoolOp(self, node):
+        operator = self.boolops[node.op.__class__.__name__]
+        operator_precedence = self.boolop_precedence[operator]
+
+        def increasing_level_traverse(node):
+            nonlocal operator_precedence
+            operator_precedence = operator_precedence.next()
+            self.set_precedence(operator_precedence, node)
+            self.traverse(node)
+
+        with self.require_parens(operator_precedence, node):
+            s = f" {operator} "
+            self.interleave(lambda: self.write(s), increasing_level_traverse, node.values)
+
+    def visit_Attribute(self, node):
+        self.set_precedence(_Precedence.ATOM, node.value)
+        self.traverse(node.value)
+        # Special case: 3.__abs__() is a syntax error, so if node.value
+        # is an integer literal then we need to either parenthesize
+        # it or add an extra space to get 3 .__abs__().
+        if isinstance(node.value, Constant) and isinstance(node.value.value, int):
+            self.write(" ")
+        self.write(".")
+        self.write(node.attr)
+
+    def visit_Call(self, node):
+        self.set_precedence(_Precedence.ATOM, node.func)
+        self.traverse(node.func)
+        with self.delimit("(", ")"):
+            comma = False
+            for e in node.args:
+                if comma:
+                    self.write(", ")
+                else:
+                    comma = True
+                self.traverse(e)
+            for e in node.keywords:
+                if comma:
+                    self.write(", ")
+                else:
+                    comma = True
+                self.traverse(e)
+
+    def visit_Subscript(self, node):
+        def is_non_empty_tuple(slice_value):
+            return (
+                isinstance(slice_value, Tuple)
+                and slice_value.elts
+            )
+
+        self.set_precedence(_Precedence.ATOM, node.value)
+        self.traverse(node.value)
+        with self.delimit("[", "]"):
+            if is_non_empty_tuple(node.slice):
+                # parentheses can be omitted if the tuple isn't empty
+                self.items_view(self.traverse, node.slice.elts)
+            else:
+                self.traverse(node.slice)
+
+    def visit_Starred(self, node):
+        self.write("*")
+        self.set_precedence(_Precedence.EXPR, node.value)
+        self.traverse(node.value)
+
+    def visit_Ellipsis(self, node):
+        self.write("...")
+
+    def visit_Slice(self, node):
+        if node.lower:
+            self.traverse(node.lower)
+        self.write(":")
+        if node.upper:
+            self.traverse(node.upper)
+        if node.step:
+            self.write(":")
+            self.traverse(node.step)
+
+    def visit_Match(self, node):
+        self.fill("match ")
+        self.traverse(node.subject)
+        with self.block():
+            for case in node.cases:
+                self.traverse(case)
+
+    def visit_arg(self, node):
+        self.write(node.arg)
+        if node.annotation:
+            self.write(": ")
+            self.traverse(node.annotation)
+
+    def visit_arguments(self, node):
+        first = True
+        # normal arguments
+        all_args = node.posonlyargs + node.args
+        defaults = [None] * (len(all_args) - len(node.defaults)) + node.defaults
+        for index, elements in enumerate(zip(all_args, defaults), 1):
+            a, d = elements
+            if first:
+                first = False
+            else:
+                self.write(", ")
+            self.traverse(a)
+            if d:
+                self.write("=")
+                self.traverse(d)
+            if index == len(node.posonlyargs):
+                self.write(", /")
+
+        # varargs, or bare '*' if no varargs but keyword-only arguments present
+        if node.vararg or node.kwonlyargs:
+            if first:
+                first = False
+            else:
+                self.write(", ")
+            self.write("*")
+            if node.vararg:
+                self.write(node.vararg.arg)
+                if node.vararg.annotation:
+                    self.write(": ")
+                    self.traverse(node.vararg.annotation)
+
+        # keyword-only arguments
+        if node.kwonlyargs:
+            for a, d in zip(node.kwonlyargs, node.kw_defaults):
+                self.write(", ")
+                self.traverse(a)
+                if d:
+                    self.write("=")
+                    self.traverse(d)
+
+        # kwargs
+        if node.kwarg:
+            if first:
+                first = False
+            else:
+                self.write(", ")
+            self.write("**" + node.kwarg.arg)
+            if node.kwarg.annotation:
+                self.write(": ")
+                self.traverse(node.kwarg.annotation)
+
+    def visit_keyword(self, node):
+        if node.arg is None:
+            self.write("**")
+        else:
+            self.write(node.arg)
+            self.write("=")
+        self.traverse(node.value)
+
+    def visit_Lambda(self, node):
+        with self.require_parens(_Precedence.TEST, node):
+            self.write("lambda")
+            with self.buffered() as buffer:
+                self.traverse(node.args)
+            if buffer:
+                self.write(" ", *buffer)
+            self.write(": ")
+            self.set_precedence(_Precedence.TEST, node.body)
+            self.traverse(node.body)
+
+    def visit_alias(self, node):
+        self.write(node.name)
+        if node.asname:
+            self.write(" as " + node.asname)
+
+    def visit_withitem(self, node):
+        self.traverse(node.context_expr)
+        if node.optional_vars:
+            self.write(" as ")
+            self.traverse(node.optional_vars)
+
+    def visit_match_case(self, node):
+        self.fill("case ")
+        self.traverse(node.pattern)
+        if node.guard:
+            self.write(" if ")
+            self.traverse(node.guard)
+        with self.block():
+            self.traverse(node.body)
+
+    def visit_MatchValue(self, node):
+        self.traverse(node.value)
+
+    def visit_MatchSingleton(self, node):
+        self._write_constant(node.value)
+
+    def visit_MatchSequence(self, node):
+        with self.delimit("[", "]"):
+            self.interleave(
+                lambda: self.write(", "), self.traverse, node.patterns
+            )
+
+    def visit_MatchStar(self, node):
+        name = node.name
+        if name is None:
+            name = "_"
+        self.write(f"*{name}")
+
+    def visit_MatchMapping(self, node):
+        def write_key_pattern_pair(pair):
+            k, p = pair
+            self.traverse(k)
+            self.write(": ")
+            self.traverse(p)
+
+        with self.delimit("{", "}"):
+            keys = node.keys
+            self.interleave(
+                lambda: self.write(", "),
+                write_key_pattern_pair,
+                zip(keys, node.patterns, strict=True),
+            )
+            rest = node.rest
+            if rest is not None:
+                if keys:
+                    self.write(", ")
+                self.write(f"**{rest}")
+
+    def visit_MatchClass(self, node):
+        self.set_precedence(_Precedence.ATOM, node.cls)
+        self.traverse(node.cls)
+        with self.delimit("(", ")"):
+            patterns = node.patterns
+            self.interleave(
+                lambda: self.write(", "), self.traverse, patterns
+            )
+            attrs = node.kwd_attrs
+            if attrs:
+                def write_attr_pattern(pair):
+                    attr, pattern = pair
+                    self.write(f"{attr}=")
+                    self.traverse(pattern)
+
+                if patterns:
+                    self.write(", ")
+                self.interleave(
+                    lambda: self.write(", "),
+                    write_attr_pattern,
+                    zip(attrs, node.kwd_patterns, strict=True),
+                )
+
+    def visit_MatchAs(self, node):
+        name = node.name
+        pattern = node.pattern
+        if name is None:
+            self.write("_")
+        elif pattern is None:
+            self.write(node.name)
+        else:
+            with self.require_parens(_Precedence.TEST, node):
+                self.set_precedence(_Precedence.BOR, node.pattern)
+                self.traverse(node.pattern)
+                self.write(f" as {node.name}")
+
+    def visit_MatchOr(self, node):
+        with self.require_parens(_Precedence.BOR, node):
+            self.set_precedence(_Precedence.BOR.next(), *node.patterns)
+            self.interleave(lambda: self.write(" | "), self.traverse, node.patterns)
+
+def unparse(ast_obj):
+    unparser = _Unparser()
+    return unparser.visit(ast_obj)
+
+
+def main():
+    import argparse
+
+    parser = argparse.ArgumentParser(prog='python -m ast')
+    parser.add_argument('infile', type=argparse.FileType(mode='rb'), nargs='?',
+                        default='-',
+                        help='the file to parse; defaults to stdin')
+    parser.add_argument('-m', '--mode', default='exec',
+                        choices=('exec', 'single', 'eval', 'func_type'),
+                        help='specify what kind of code must be parsed')
+    parser.add_argument('--no-type-comments', default=True, action='store_false',
+                        help="don't add information about type comments")
+    parser.add_argument('-a', '--include-attributes', action='store_true',
+                        help='include attributes such as line numbers and '
+                             'column offsets')
+    parser.add_argument('-i', '--indent', type=int, default=3,
+                        help='indentation of nodes (number of spaces)')
+    args = parser.parse_args()
+
+    with args.infile as infile:
+        source = infile.read()
+    tree = parse(source, args.infile.name, args.mode, type_comments=args.no_type_comments)
+    print(dump(tree, include_attributes=args.include_attributes, indent=args.indent))
+
+if __name__ == '__main__':
+    main()