code: def test_init_and_stop(self):
      self.ray_ctx.init()
      actors = [TestRay.remote() for i in range(0, self.node_num)]
      print(ray.get([actor.hostname.remote() for actor in actors]))
      self.ray_ctx.stop()
      assert (
          not self.ray_ctx.initialized
      ), "The Ray cluster has been stopped."
      time.sleep(3)
  
file_path: BigDL/python/orca/test/bigdl/orca/ray/ray_cluster/test_rayctx_reinit.py
imports: import time
  from unittest import TestCase
  import numpy
  import pytest
  import ray
  from bigdl.orca.ray import OrcaRayContext
  from bigdl.orca.common import stop_orca_context
label_desc: Use image node_id 3 for calling the TestUtil obj's underlying member method code with example usage: obj.test_init_and_stop() without return types