code: def cancel_tasks(self):
      # cancel listening for all clients
      _ = [task.cancel() for task in self._clients.values()]
  
file_path: mars/mars/oscar/backends/core.py
imports: import asyncio
  import copy
  import logging
  from typing import Dict, Union
  from ...oscar.profiling import ProfilingData
  from ...utils import Timer
  from ..errors import ServerClosed
  from .communication import Client
  from .message import _MessageBase, ResultMessage, ErrorMessage, DeserializeMessageFailed
  from .router import Router
label_desc: Use image node_id 2 for calling the ActorCaller obj's underlying member method code with example usage: obj.cancel_tasks() without return types