code: def test_nested_actors(serve_instance):
      signal = SignalActor.remote()
  
      @ray.remote(num_cpus=1)
      class CustomActor:
          def __init__(self) -> None:
              signal.send.remote()
  
      @serve.deployment
      class A:
          def __init__(self) -> None:
              self.a = CustomActor.remote()
  
      serve.run(A.bind())
  
      # The nested actor should start successfully.
      ray.get(signal.wait.remote(), timeout=10)
  
imports: import asyncio
  import gc
  import sys
  import numpy
  import pytest
  import requests
  from fastapi import FastAPI
  from fastapi.responses import JSONResponse
  import ray
  from ray import serve
  from ray._private.test_utils import SignalActor
  from ray.serve.context import _get_global_client
  from ray.serve.handle import DeploymentHandle
label_desc: Use image node_id 6 for calling a global function with example usage: test_nested_actors(serve_instance) without return types