docs: def value(self, item):
          # type: (Any) -> Any
          """
          Return value stored in weakref.
          :param item: Object from which get the value.
          :return: Value stored in the weakref, otherwise original value.
          :raise TreeDeletedException: when weakref is already deleted.
          """
          if isinstance(item, weakref.ReferenceType):
              if item() is None:
                  raise TreeDeletedException()
              return item()
          return item