code: def test_ray_start_and_stop():
      for i in range(10):
          subprocess.check_call(["ray", "start", "--head"])
          subprocess.check_call(["ray", "stop"])
  
imports: import mock
  import subprocess
  import sys
  import pytest
  import ray
  from ray._raylet import check_health
  from ray._private.test_utils import Semaphore, client_test_enabled, wait_for_condition, get_gcs_memory_used
  from ray.experimental.internal_kv import _internal_kv_list
label_desc: Use image node_id 4 for calling a global function with example usage: test_ray_start_and_stop() without return types