code: def append_child(self, child):
      self._children.append(child)
  
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 5 for calling the AbstractExpression obj's underlying member method code with example usage: obj.append_child(child) without return types