class_docstr: A task runner that runs an asyncio event loop on a background thread.
code: def _runner(self) -> None:
      loop = self.__io_loop
      assert loop is not None
      try:
          loop.run_forever()
      finally:
          loop.close()
  
imports: from __future__ import annotations
  import asyncio
  import atexit
  import errno
  import inspect
  import sys
  import threading
  import warnings
  from contextvars import ContextVar
  from pathlib import Path
  from types import FrameType
  from typing import Any, Awaitable, Callable, TypeVar, cast
label_desc: Use image node_id 3 for calling the _TaskRunner obj's underlying member method code with example usage: obj._runner() without return types