class_docstr: Wrapper around `History` implementations that run the `load()` generator in
  a thread.
  
  Use this to increase the start-up time of prompt_toolkit applications.
  History entries are available as soon as they are loaded. We don't have to
  wait for everything to be loaded.
code: def load_history_strings(self) -> Iterable[str]:
      return self.history.load_history_strings()
  
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 4 for calling the ThreadedHistory obj's underlying member method code with example usage: obj.load_history_strings() and returns: self