class_docstr: World Runner.
  
  Launches worlds, overworlds, etc. Helper for ChatServiceManager.
docstr: Shutdown the world runner.
docstr_tok: ["Shutdown","the","world","runner","."]
code: def shutdown(self):
      """
      Shutdown the world runner.
      """
      for _, task in self.tasks.items():
          if task.world is not None:
              task.world.shutdown()
  
      self.system_done = (
          True  # this forces worlds to stop executing parley
      )
      self._log("Executor shutting down.")
      self.executor.shutdown()
      self._log("Shutdown complete.")
  
file_path: ParlAI/parlai/chat_service/core/world_runner.py
imports: import logging
  import time
  import datetime
  from concurrent import futures
  import parlai.chat_service.utils.logging
  import parlai.chat_service.utils.misc
label_desc: Use image node_id 4 for calling the ChatServiceWorldRunner obj's underlying member method code with example usage: obj.shutdown() without return types