code: def test_stop(self):
      self.ray_ctx.stop()
      assert (
          not self.ray_ctx.initialized
      ), "The Ray cluster has been stopped."
  
file_path: BigDL/python/orca/test/bigdl/orca/ray/ray_cluster/test_rayctx_local.py
imports: from unittest import TestCase
  import pytest
  import ray
  from bigdl.orca import stop_orca_context
  from bigdl.orca.ray import OrcaRayContext
label_desc: Use image node_id 4 for calling the TestUtil obj's underlying member method code with example usage: obj.test_stop() without return types