code: def is_runner_free(self):
      return self._running_processor is None
  
file_path: mars/mars/services/subtask/worker/runner.py
imports: import asyncio
  import importlib
  import logging
  from typing import Dict, Optional, Type
  from ....None import oscar
  from ....lib.aio import alru_cache
  from ....typing import BandType
  from ...cluster import ClusterAPI
  from ..core import Subtask, SubtaskResult
  from ..errors import SlotOccupiedAlready
  from .processor import SubtaskProcessor, SubtaskProcessorActor
label_desc: Use image node_id 4 for calling the SubtaskRunnerActor obj's underlying member method code with example usage: obj.is_runner_free() and returns: unknown