code: def stop(self) -> None:
      if not self.initialized:
          print("The Ray cluster has not been launched.")
          return
      import ray
  
      ray.shutdown()
      self.initialized = False
  
imports: import os
  import re
  import subprocess
  import time
  import uuid
  import random
  import warnings
  import tempfile
  import filelock
  import multiprocessing
  from packaging import version
  from bigdl.orca.ray.process import session_execute, ProcessMonitor
  from bigdl.orca.ray.utils import is_local
  from bigdl.orca.ray.utils import resource_to_bytes
  from bigdl.orca.ray.utils import get_parent_pid
  from bigdl.dllib.utils.log4Error import invalidInputError
  from typing import TYPE_CHECKING
  from typing import Any, Dict, Optional, List
label_desc: Use image node_id 5 for calling the RayOnSparkContext obj's underlying member method code with example usage: obj.stop() without return types