text: """Weak reference support for Python.
  
  This module is an implementation of PEP 205:
  
  https://www.python.org/dev/peps/pep-0205/
  """
  
  # Naming convention: Variables named "wr" are weak reference objects;
  # they are called this instead of "ref" to avoid name collisions with
  # the module-global ref() function imported from _weakref.
  
  from _weakref import (
       getweakrefcount,
       getweakrefs,
       ref,
       proxy,
       CallableProxyType,
       ProxyType,
       ReferenceType,
       _remove_dead_weakref)
  
  from _weakrefset import WeakSet, _IterationGuard
  
  import _collections_abc  # Import after _weakref to avoid circular import.
  import sys
  import itertools
  
  ProxyTypes = (ProxyType, CallableProxyType)
  
  __all__ = ["ref", "proxy", "getweakrefcount", "getweakrefs",
             "WeakKeyDictionary", "ReferenceType", "ProxyType",
             "CallableProxyType", "ProxyTypes", "WeakValueDictionary",
             "WeakSet", "WeakMethod", "finalize"]
  
  
  _collections_abc.Set.register(WeakSet)
  _collections_abc.MutableSet.register(WeakSet)
  
  class WeakMethod(ref):
      """
      A custom `weakref.ref` subclass which simulates a weak reference to
      a bound method, working around the lifetime problem of bound methods.
      """
  
      __slots__ = "_func_ref", "_meth_type", "_alive", "__weakref__"
  
      def __new__(cls, meth, callback=None):
          try:
              obj = meth.__self__
              func = meth.__func__
          except AttributeError:
              raise TypeError("argument should be a bound method, not {}"
                              .format(type(meth))) from None
          def _cb(arg):
              # The self-weakref trick is needed to avoid creating a reference
              # cycle.
              self = self_wr()
              if self._alive:
                  self._alive = False
                  if callback is not None:
                      callback(self)
          self = ref.__new__(cls, obj, _cb)
          self._func_ref = ref(func, _cb)
          self._meth_type = type(meth)
          self._alive = True
          self_wr = ref(self)
          return self
  
      def __call__(self):
          obj = super().__call__()
          func = self._func_ref()
          if obj is None or func is None:
              return None
          return self._meth_type(func, obj)
  
      def __eq__(self, other):
          if isinstance(other, WeakMethod):
              if not self._alive or not other._alive:
                  return self is other
              return ref.__eq__(self, other) and self._func_ref == other._func_ref
          return NotImplemented
  
      def __ne__(self, other):
          if isinstance(other, WeakMethod):
              if not self._alive or not other._alive:
                  return self is not other
              return ref.__ne__(self, other) or self._func_ref != other._func_ref
          return NotImplemented
  
      __hash__ = ref.__hash__
  
  
  class WeakValueDictionary(_collections_abc.MutableMapping):
      """Mapping class that references values weakly.
  
      Entries in the dictionary will be discarded when no strong
      reference to the value exists anymore
      """
      # We inherit the constructor without worrying about the input
      # dictionary; since it uses our .update() method, we get the right
      # checks (if the other dictionary is a WeakValueDictionary,
      # objects are unwrapped on the way out, and we always wrap on the
      # way in).
  
      def __init__(self, other=(), /, **kw):
          def remove(wr, selfref=ref(self), _atomic_removal=_remove_dead_weakref):
              self = selfref()
              if self is not None:
                  if self._iterating:
                      self._pending_removals.append(wr.key)
                  else:
                      # Atomic removal is necessary since this function
                      # can be called asynchronously by the GC
                      _atomic_removal(self.data, wr.key)
          self._remove = remove
          # A list of keys to be removed
          self._pending_removals = []
          self._iterating = set()
          self.data = {}
          self.update(other, **kw)
  
      def _commit_removals(self, _atomic_removal=_remove_dead_weakref):
          pop = self._pending_removals.pop
          d = self.data
          # We shouldn't encounter any KeyError, because this method should
          # always be called *before* mutating the dict.
          while True:
              try:
                  key = pop()
              except IndexError:
                  return
              _atomic_removal(d, key)
  
      def __getitem__(self, key):
          if self._pending_removals:
              self._commit_removals()
          o = self.data[key]()
          if o is None:
              raise KeyError(key)
          else:
              return o
  
      def __delitem__(self, key):
          if self._pending_removals:
              self._commit_removals()
          del self.data[key]
  
      def __len__(self):
          if self._pending_removals:
              self._commit_removals()
          return len(self.data)
  
      def __contains__(self, key):
          if self._pending_removals:
              self._commit_removals()
          try:
              o = self.data[key]()
          except KeyError:
              return False
          return o is not None
  
      def __repr__(self):
          return "<%s at %#x>" % (self.__class__.__name__, id(self))
  
      def __setitem__(self, key, value):
          if self._pending_removals:
              self._commit_removals()
          self.data[key] = KeyedRef(value, self._remove, key)
  
      def copy(self):
          if self._pending_removals:
              self._commit_removals()
          new = WeakValueDictionary()
          with _IterationGuard(self):
              for key, wr in self.data.items():
                  o = wr()
                  if o is not None:
                      new[key] = o
          return new
  
      __copy__ = copy
  
      def __deepcopy__(self, memo):
          from copy import deepcopy
          if self._pending_removals:
              self._commit_removals()
          new = self.__class__()
          with _IterationGuard(self):
              for key, wr in self.data.items():
                  o = wr()
                  if o is not None:
                      new[deepcopy(key, memo)] = o
          return new
  
      def get(self, key, default=None):
          if self._pending_removals:
              self._commit_removals()
          try:
              wr = self.data[key]
          except KeyError:
              return default
          else:
              o = wr()
              if o is None:
                  # This should only happen
                  return default
              else:
                  return o
  
      def items(self):
          if self._pending_removals:
              self._commit_removals()
          with _IterationGuard(self):
              for k, wr in self.data.items():
                  v = wr()
                  if v is not None:
                      yield k, v
  
      def keys(self):
          if self._pending_removals:
              self._commit_removals()
          with _IterationGuard(self):
              for k, wr in self.data.items():
                  if wr() is not None:
                      yield k
  
      __iter__ = keys
  
      def itervaluerefs(self):
          """Return an iterator that yields the weak references to the values.
  
          The references are not guaranteed to be 'live' at the time
          they are used, so the result of calling the references needs
          to be checked before being used.  This can be used to avoid
          creating references that will cause the garbage collector to
          keep the values around longer than needed.
  
          """
          if self._pending_removals:
              self._commit_removals()
          with _IterationGuard(self):
              yield from self.data.values()
  
      def values(self):
          if self._pending_removals:
              self._commit_removals()
          with _IterationGuard(self):
              for wr in self.data.values():
                  obj = wr()
                  if obj is not None:
                      yield obj
  
      def popitem(self):
          if self._pending_removals:
              self._commit_removals()
          while True:
              key, wr = self.data.popitem()
              o = wr()
              if o is not None:
                  return key, o
  
      def pop(self, key, *args):
          if self._pending_removals:
              self._commit_removals()
          try:
              o = self.data.pop(key)()
          except KeyError:
              o = None
          if o is None:
              if args:
                  return args[0]
              else:
                  raise KeyError(key)
          else:
              return o
  
      def setdefault(self, key, default=None):
          try:
              o = self.data[key]()
          except KeyError:
              o = None
          if o is None:
              if self._pending_removals:
                  self._commit_removals()
              self.data[key] = KeyedRef(default, self._remove, key)
              return default
          else:
              return o
  
      def update(self, other=None, /, **kwargs):
          if self._pending_removals:
              self._commit_removals()
          d = self.data
          if other is not None:
              if not hasattr(other, "items"):
                  other = dict(other)
              for key, o in other.items():
                  d[key] = KeyedRef(o, self._remove, key)
          for key, o in kwargs.items():
              d[key] = KeyedRef(o, self._remove, key)
  
      def valuerefs(self):
          """Return a list of weak references to the values.
  
          The references are not guaranteed to be 'live' at the time
          they are used, so the result of calling the references needs
          to be checked before being used.  This can be used to avoid
          creating references that will cause the garbage collector to
          keep the values around longer than needed.
  
          """
          if self._pending_removals:
              self._commit_removals()
          return list(self.data.values())
  
      def __ior__(self, other):
          self.update(other)
          return self
  
      def __or__(self, other):
          if isinstance(other, _collections_abc.Mapping):
              c = self.copy()
              c.update(other)
              return c
          return NotImplemented
  
      def __ror__(self, other):
          if isinstance(other, _collections_abc.Mapping):
              c = self.__class__()
              c.update(other)
              c.update(self)
              return c
          return NotImplemented
  
  
  class KeyedRef(ref):
      """Specialized reference that includes a key corresponding to the value.
  
      This is used in the WeakValueDictionary to avoid having to create
      a function object for each key stored in the mapping.  A shared
      callback object can use the 'key' attribute of a KeyedRef instead
      of getting a reference to the key from an enclosing scope.
  
      """
  
      __slots__ = "key",
  
      def __new__(type, ob, callback, key):
          self = ref.__new__(type, ob, callback)
          self.key = key
          return self
  
      def __init__(self, ob, callback, key):
          super().__init__(ob, callback)
  
  
  class WeakKeyDictionary(_collections_abc.MutableMapping):
      """ Mapping class that references keys weakly.
  
      Entries in the dictionary will be discarded when there is no
      longer a strong reference to the key. This can be used to
      associate additional data with an object owned by other parts of
      an application without adding attributes to those objects. This
      can be especially useful with objects that override attribute
      accesses.
      """
  
      def __init__(self, dict=None):
          self.data = {}
          def remove(k, selfref=ref(self)):
              self = selfref()
              if self is not None:
                  if self._iterating:
                      self._pending_removals.append(k)
                  else:
                      try:
                          del self.data[k]
                      except KeyError:
                          pass
          self._remove = remove
          # A list of dead weakrefs (keys to be removed)
          self._pending_removals = []
          self._iterating = set()
          self._dirty_len = False
          if dict is not None:
              self.update(dict)
  
      def _commit_removals(self):
          # NOTE: We don't need to call this method before mutating the dict,
          # because a dead weakref never compares equal to a live weakref,
          # even if they happened to refer to equal objects.
          # However, it means keys may already have been removed.
          pop = self._pending_removals.pop
          d = self.data
          while True:
              try:
                  key = pop()
              except IndexError:
                  return
  
              try:
                  del d[key]
              except KeyError:
                  pass
  
      def _scrub_removals(self):
          d = self.data
          self._pending_removals = [k for k in self._pending_removals if k in d]
          self._dirty_len = False
  
      def __delitem__(self, key):
          self._dirty_len = True
          del self.data[ref(key)]
  
      def __getitem__(self, key):
          return self.data[ref(key)]
  
      def __len__(self):
          if self._dirty_len and self._pending_removals:
              # self._pending_removals may still contain keys which were
              # explicitly removed, we have to scrub them (see issue #21173).
              self._scrub_removals()
          return len(self.data) - len(self._pending_removals)
  
      def __repr__(self):
          return "<%s at %#x>" % (self.__class__.__name__, id(self))
  
      def __setitem__(self, key, value):
          self.data[ref(key, self._remove)] = value
  
      def copy(self):
          new = WeakKeyDictionary()
          with _IterationGuard(self):
              for key, value in self.data.items():
                  o = key()
                  if o is not None:
                      new[o] = value
          return new
  
      __copy__ = copy
  
      def __deepcopy__(self, memo):
          from copy import deepcopy
          new = self.__class__()
          with _IterationGuard(self):
              for key, value in self.data.items():
                  o = key()
                  if o is not None:
                      new[o] = deepcopy(value, memo)
          return new
  
      def get(self, key, default=None):
          return self.data.get(ref(key),default)
  
      def __contains__(self, key):
          try:
              wr = ref(key)
          except TypeError:
              return False
          return wr in self.data
  
      def items(self):
          with _IterationGuard(self):
              for wr, value in self.data.items():
                  key = wr()
                  if key is not None:
                      yield key, value
  
      def keys(self):
          with _IterationGuard(self):
              for wr in self.data:
                  obj = wr()
                  if obj is not None:
                      yield obj
  
      __iter__ = keys
  
      def values(self):
          with _IterationGuard(self):
              for wr, value in self.data.items():
                  if wr() is not None:
                      yield value
  
      def keyrefs(self):
          """Return a list of weak references to the keys.
  
          The references are not guaranteed to be 'live' at the time
          they are used, so the result of calling the references needs
          to be checked before being used.  This can be used to avoid
          creating references that will cause the garbage collector to
          keep the keys around longer than needed.
  
          """
          return list(self.data)
  
      def popitem(self):
          self._dirty_len = True
          while True:
              key, value = self.data.popitem()
              o = key()
              if o is not None:
                  return o, value
  
      def pop(self, key, *args):
          self._dirty_len = True
          return self.data.pop(ref(key), *args)
  
      def setdefault(self, key, default=None):
          return self.data.setdefault(ref(key, self._remove),default)
  
      def update(self, dict=None, /, **kwargs):
          d = self.data
          if dict is not None:
              if not hasattr(dict, "items"):
                  dict = type({})(dict)
              for key, value in dict.items():
                  d[ref(key, self._remove)] = value
          if len(kwargs):
              self.update(kwargs)
  
      def __ior__(self, other):
          self.update(other)
          return self
  
      def __or__(self, other):
          if isinstance(other, _collections_abc.Mapping):
              c = self.copy()
              c.update(other)
              return c
          return NotImplemented
  
      def __ror__(self, other):
          if isinstance(other, _collections_abc.Mapping):
              c = self.__class__()
              c.update(other)
              c.update(self)
              return c
          return NotImplemented
  
  
  class finalize:
      """Class for finalization of weakrefable objects
  
      finalize(obj, func, *args, **kwargs) returns a callable finalizer
      object which will be called when obj is garbage collected. The
      first time the finalizer is called it evaluates func(*arg, **kwargs)
      and returns the result. After this the finalizer is dead, and
      calling it just returns None.
  
      When the program exits any remaining finalizers for which the
      atexit attribute is true will be run in reverse order of creation.
      By default atexit is true.
      """
  
      # Finalizer objects don't have any state of their own.  They are
      # just used as keys to lookup _Info objects in the registry.  This
      # ensures that they cannot be part of a ref-cycle.
  
      __slots__ = ()
      _registry = {}
      _shutdown = False
      _index_iter = itertools.count()
      _dirty = False
      _registered_with_atexit = False
  
      class _Info:
          __slots__ = ("weakref", "func", "args", "kwargs", "atexit", "index")
  
      def __init__(self, obj, func, /, *args, **kwargs):
          if not self._registered_with_atexit:
              # We may register the exit function more than once because
              # of a thread race, but that is harmless
              import atexit
              atexit.register(self._exitfunc)
              finalize._registered_with_atexit = True
          info = self._Info()
          info.weakref = ref(obj, self)
          info.func = func
          info.args = args
          info.kwargs = kwargs or None
          info.atexit = True
          info.index = next(self._index_iter)
          self._registry[self] = info
          finalize._dirty = True
  
      def __call__(self, _=None):
          """If alive then mark as dead and return func(*args, **kwargs);
          otherwise return None"""
          info = self._registry.pop(self, None)
          if info and not self._shutdown:
              return info.func(*info.args, **(info.kwargs or {}))
  
      def detach(self):
          """If alive then mark as dead and return (obj, func, args, kwargs);
          otherwise return None"""
          info = self._registry.get(self)
          obj = info and info.weakref()
          if obj is not None and self._registry.pop(self, None):
              return (obj, info.func, info.args, info.kwargs or {})
  
      def peek(self):
          """If alive then return (obj, func, args, kwargs);
          otherwise return None"""
          info = self._registry.get(self)
          obj = info and info.weakref()
          if obj is not None:
              return (obj, info.func, info.args, info.kwargs or {})
  
      @property
      def alive(self):
          """Whether finalizer is alive"""
          return self in self._registry
  
      @property
      def atexit(self):
          """Whether finalizer should be called at exit"""
          info = self._registry.get(self)
          return bool(info) and info.atexit
  
      @atexit.setter
      def atexit(self, value):
          info = self._registry.get(self)
          if info:
              info.atexit = bool(value)
  
      def __repr__(self):
          info = self._registry.get(self)
          obj = info and info.weakref()
          if obj is None:
              return '<%s object at %#x; dead>' % (type(self).__name__, id(self))
          else:
              return '<%s object at %#x; for %r at %#x>' % \
                  (type(self).__name__, id(self), type(obj).__name__, id(obj))
  
      @classmethod
      def _select_for_exit(cls):
          # Return live finalizers marked for exit, oldest first
          L = [(f,i) for (f,i) in cls._registry.items() if i.atexit]
          L.sort(key=lambda item:item[1].index)
          return [f for (f,i) in L]
  
      @classmethod
      def _exitfunc(cls):
          # At shutdown invoke finalizers for which atexit is true.
          # This is called once all other non-daemonic threads have been
          # joined.
          reenable_gc = False
          try:
              if cls._registry:
                  import gc
                  if gc.isenabled():
                      reenable_gc = True
                      gc.disable()
                  pending = None
                  while True:
                      if pending is None or finalize._dirty:
                          pending = cls._select_for_exit()
                          finalize._dirty = False
                      if not pending:
                          break
                      f = pending.pop()
                      try:
                          # gc is disabled, so (assuming no daemonic
                          # threads) the following is the only line in
                          # this function which might trigger creation
                          # of a new finalizer
                          f()
                      except Exception:
                          sys.excepthook(*sys.exc_info())
                      assert f not in cls._registry
          finally:
              # prevent any more finalizers from executing during shutdown
              finalize._shutdown = True
              if reenable_gc:
                  gc.enable()
  