code: def test_idempotent_disconnect(init_and_serve):
      from ray.util.client import ray
  
      ray.disconnect()
      ray.disconnect()
      ray.connect("localhost:50051")
      ray.disconnect()
      ray.disconnect()
  
imports: import pytest
  import time
  import random
  import sys
  import subprocess
  from unittest.mock import patch
  import ray.util.client.server.server
  import ray.core.generated.ray_client_pb2
  from ray.util.client import _ClientContext, CURRENT_PROTOCOL_VERSION
  from ray.cluster_utils import cluster_not_supported
  import ray
label_desc: Use image node_id 6 for calling a global function with example usage: test_idempotent_disconnect(init_and_serve) without return types