code: def __enter__(self):
      w = self.weakcontainer()
      if w is not None:
          w._iterating.add(self)
      return self
  
imports: from _weakref import ref
  from types import GenericAlias
label_desc: Use image node_id 2 for calling the _IterationGuard obj's underlying member method code with example usage: obj.__enter__() and returns: self