text: """
      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
  
  
  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):
      """
      Safely evaluate an expression node or a string containing 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.
      """
      if isinstance(node_or_string, str):
          node_or_string = parse(node_or_string, mode='eval')
      if isinstance(node_or_string, Expression):
          node_or_string = node_or_string.body
      def _raise_malformed_node(node):
          raise ValueError(f'malformed node or string: {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)
              if value is not None:
                  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):
          if 'lineno' in child._attributes:
              child.lineno = getattr(child, 'lineno', 0) + n
          if 'end_lineno' in child._attributes:
              child.end_lineno = getattr(child, 'end_lineno', 0) + 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
  
  
  # 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):
      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)
  
  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)
  
  class _Precedence(IntEnum):
      """Precedence table that originated from python grammar."""
  
      TUPLE = auto()
      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
  
  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):
          self._source = []
          self._buffer = []
          self._precedences = {}
          self._type_ignores = {}
          self._indent = 0
  
      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):
          """Append a piece of text"""
          self._source.append(text)
  
      def buffer_writer(self, text):
          self._buffer.append(text)
  
      @property
      def buffer(self):
          value = "".join(self._buffer)
          self._buffer.clear()
          return value
  
      @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)
  
      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.TUPLE, 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)
          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.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 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_ExceptHandler(self, node):
          self.fill("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.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 visit_JoinedStr(self, node):
          self.write("f")
          self._fstring_JoinedStr(node, self.buffer_writer)
          self.write(repr(self.buffer))
  
      def visit_FormattedValue(self, node):
          self.write("f")
          self._fstring_FormattedValue(node, self.buffer_writer)
          self.write(repr(self.buffer))
  
      def _fstring_JoinedStr(self, node, write):
          for value in node.values:
              meth = getattr(self, "_fstring_" + type(value).__name__)
              meth(value, write)
  
      def _fstring_Constant(self, node, write):
          if not isinstance(node.value, str):
              raise ValueError("Constants inside JoinedStr should be a string.")
          value = node.value.replace("{", "{{").replace("}", "}}")
          write(value)
  
      def _fstring_FormattedValue(self, node, write):
          write("{")
          unparser = type(self)()
          unparser.set_precedence(_Precedence.TEST.next(), node.value)
          expr = unparser.visit(node.value)
          if expr.startswith("{"):
              write(" ")  # Separate pair of opening brackets as "{ {"
          write(expr)
          if node.conversion != -1:
              conversion = chr(node.conversion)
              if conversion not in "sra":
                  raise ValueError("Unknown f-string conversion.")
              write(f"!{conversion}")
          if node.format_spec:
              write(":")
              meth = getattr(self, "_fstring_" + type(node.format_spec).__name__)
              meth(node.format_spec, write)
          write("}")
  
      def visit_Name(self, node):
          self.write(node.id)
  
      def _write_docstring(self, node):
          def esc_char(c):
              if c in ("\n", "\t"):
                  # In the AST form, we don't know the author's intentation
                  # about how this should be displayed. We'll only escape
                  # \n and \t, because they are more likely to be unescaped
                  # in the source
                  return c
              return c.encode('unicode_escape').decode('ascii')
  
          self.fill()
          if node.kind == "u":
              self.write("u")
  
          value = node.value
          if value:
              # Preserve quotes in the docstring by escaping them
              value = "".join(map(esc_char, value))
              if value[-1] == '"':
                  value = value.replace('"', '\\"', -1)
              value = value.replace('"""', '""\\"')
  
          self.write(f'"""{value}"""')
  
      def _write_constant(self, value):
          if isinstance(value, (float, complex)):
              # Substitute overflowing decimal literal for AST infinities.
              self.write(repr(value).replace("inf", _INFSTR))
          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 not node.elts:
              raise ValueError("Set node should have at least one item")
          with self.delimit("{", "}"):
              self.interleave(lambda: self.write(", "), self.traverse, node.elts)
  
      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("(", ")"):
              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 seperated
              # 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):
          self.set_precedence(_Precedence.ATOM, node.value)
          self.traverse(node.value)
          with self.delimit("[", "]"):
              if isinstance(node.slice, Tuple) and node.slice.elts:
                  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_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 ")
              self.traverse(node.args)
              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 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()
  