code: def container(self):
          
          if self.parent is None:
              return None
          elif self.location is None:
              return self.parent.content
          else:
              container = getattr(self.parent, self.location)
              if isinstance(container, (ListContainer, DictContainer)):
                  return container
              else:
                  assert self is container
docs: Rarely used attribute that returns the ``ListContainer`` or
          ``DictContainer`` that contains the element
          (or returns None if no such container exist)
  
          :rtype: ``ListContainer`` | ``DictContainer`` | ``None``