code: def test_destroy_actors(shutdown_only):
      info = ray.init(num_cpus=3, _system_config=_SYSTEM_CONFIG)
  
      @ray.remote(num_cpus=1)
      class Actor:
          def ping(self):
              pass
  
      a = Actor.remote()
      b = Actor.remote()
      c = Actor.remote()
      del a
      del b
  
      expected = {
          "ALIVE": 1,
          "DEAD": 2,
      }
      wait_for_condition(
          lambda: actors_by_state(info) == expected,
          timeout=20,
          retry_interval_ms=500,
      )
      del c
  
imports: import asyncio
  from collections import defaultdict
  import pytest
  import time
  from typing import Dict
  import ray
  from ray.util.state import list_actors
  from ray._private.test_utils import raw_metrics, wait_for_condition, run_string_as_driver
  from ray._private.worker import RayContext
label_desc: Use image node_id 4 for calling a global function with example usage: test_destroy_actors(shutdown_only) without return types