code: def global_f():
      return "Hello world!"
  
imports: import copy
  import json
  import logging
  import sys
  from typing import Dict, List, Optional, Union
  import pytest
  from ray import serve
  from ray._private.pydantic_compat import ValidationError
  from ray.serve.config import AutoscalingConfig
  from ray.serve.deployment import deployment_to_schema, schema_to_deployment
  from ray.serve.schema import DeploymentSchema, LoggingConfig, RayActorOptionsSchema, ServeApplicationSchema, ServeDeploySchema, ServeInstanceDetails
  from ray.serve.tests.common.remote_uris import TEST_DEPLOY_GROUP_PINNED_URI, TEST_MODULE_PINNED_URI
  from ray.util.accelerators.accelerators import NVIDIA_TESLA_P4, NVIDIA_TESLA_V100
label_desc: Use image node_id 5 for calling a global function with example usage: global_f() and returns: str