code: def ping_grpc_model_multiplexing(channel, app_name):
      stub = serve_pb2_grpc.UserDefinedServiceStub(channel)
      request = serve_pb2.UserDefinedMessage(
          name="foo", num=30, foo="bar"
      )
      multiplexed_model_id = "999"
      metadata = (
          ("application", app_name),
          ("multiplexed_model_id", multiplexed_model_id),
      )
      response = stub.Method2(request=request, metadata=metadata)
      assert (
          response.greeting
          == f"Method2 called model, loading model: {multiplexed_model_id}"
      )
  
imports: import asyncio
  import time
  from typing import Any, Dict
  import grpc
  import pytest
  import requests
  from starlette.requests import Request
  import ray
  from ray import serve
  from ray.actor import ActorHandle
  from ray.serve._private.constants import SERVE_NAMESPACE
  from ray.serve._private.proxy import DRAINED_MESSAGE
  from ray.serve._private.usage import ServeUsageTag
  from ray.serve._private.utils import TimerBase
  from ray.serve.generated import serve_pb2, serve_pb2_grpc
label_desc: Use image node_id 10 for calling a global function with example usage: ping_grpc_model_multiplexing(channel, app_name) without return types