code: def rtype(self) -> ExpressionReturnType:
      return self._rtype
  
imports: from abc import ABC, abstractmethod
  from collections import deque
  from copy import deepcopy
  from enum import IntEnum, auto, unique
  from typing import Any
label_desc: Use image node_id 8 for calling the AbstractExpression obj's underlying member method code with example usage: obj.rtype() and returns: self