code: def test_cold_start_time(serve_instance):
      """Test a request is served quickly by a deployment that's scaled to zero"""
  
      @serve.deployment(
          autoscaling_config={
              "min_replicas": 0,
              "max_replicas": 1,
              "look_back_period_s": 0.2,
          },
      )
      class A:
          def __call__(self):
              return "hello"
  
      handle = serve.run(A.bind())
  
      def check_running():
          assert (
              serve.status().applications["default"].status == "RUNNING"
          )
          return True
  
      wait_for_condition(check_running)
  
      start = time.time()
      result = handle.remote().result()
      cold_start_time = time.time() - start
      assert cold_start_time < 3
      print(
          "Time taken for deployment at 0 replicas to serve first request:",
          cold_start_time,
      )
      assert result == "hello"
  
imports: import asyncio
  import logging
  import os
  import sys
  import tempfile
  import time
  import zipfile
  from typing import Dict, Iterable, List
  from unittest import mock
  import pytest
  import requests
  import ray
  import ray.util.state
  from ray import serve
  from ray._private.test_utils import SignalActor, wait_for_condition
  from ray.serve._private.common import ApplicationStatus, DeploymentID, DeploymentStatus, DeploymentStatusInfo, DeploymentStatusTrigger, ReplicaState
  from ray.serve._private.constants import SERVE_DEFAULT_APP_NAME, SERVE_NAMESPACE
  from ray.serve._private.controller import ServeController
  from ray.serve.config import AutoscalingConfig
  from ray.serve.generated.serve_pb2 import DeploymentStatusInfo
  from ray.serve.schema import ServeDeploySchema
label_desc: Use image node_id 14 for calling a global function with example usage: test_cold_start_time(serve_instance) and returns: True, str