class_docstr: :class:`.History` object that doesn't remember anything.
code: def append_string(self, string: str) -> None:
      # Don't remember this.
      pass
  
imports: from __future__ import annotations
  import datetime
  import os
  import threading
  from abc import ABCMeta, abstractmethod
  from asyncio import get_running_loop
  from typing import AsyncGenerator, Iterable, Sequence
label_desc: Use image node_id 3 for calling the DummyHistory obj's underlying member method code with example usage: obj.append_string(string) without return types