code: def test_multiplexed_metrics(serve_start_shutdown):
      """Tests multiplexed API corresponding metrics."""
  
      @serve.deployment
      class Model:
          @serve.multiplexed(max_num_models_per_replica=2)
          async def get_model(self, model_id: str):
              return model_id
  
          async def __call__(self, model_id: str):
              await self.get_model(model_id)
              return
  
      handle = serve.run(Model.bind(), name="app", route_prefix="/app")
      handle.remote("model1")
      handle.remote("model2")
      # Trigger model eviction.
      handle.remote("model3")
      expected_metrics = [
          "serve_multiplexed_model_load_latency_ms",
          "serve_multiplexed_model_unload_latency_ms",
          "serve_num_multiplexed_models",
          "serve_multiplexed_models_load_counter",
          "serve_multiplexed_models_unload_counter",
      ]
  
      def verify_metrics():
          try:
              resp = requests.get("http://127.0.0.1:9999").text
          # Requests will fail if we are crashing the controller
          except requests.ConnectionError:
              return False
          for metric in expected_metrics:
              assert metric in resp
          return True
  
      wait_for_condition(
          verify_metrics,
          timeout=40,
          retry_interval_ms=1000,
      )
  
imports: import os
  import sys
  from typing import DefaultDict, Dict, List, Optional
  import grpc
  import pytest
  import requests
  from fastapi import FastAPI
  import ray
  import ray.util.state
  from ray import serve
  from ray._private.test_utils import SignalActor, wait_for_condition
  from ray.serve._private.constants import DEFAULT_LATENCY_BUCKET_MS
  from ray.serve._private.long_poll import LongPollHost, UpdatedObject
  from ray.serve._private.test_utils import ping_fruit_stand, ping_grpc_call_method, ping_grpc_list_applications
  from ray.serve._private.utils import block_until_http_ready
  from ray.serve.config import gRPCOptions
  from ray.serve.handle import DeploymentHandle
  from ray.serve.metrics import Counter, Gauge, Histogram
  from ray.serve.tests.test_config_files.grpc_deployment import g, g2
label_desc: Use image node_id 9 for calling a global function with example usage: test_multiplexed_metrics(serve_start_shutdown) and returns: True, model_id, False