code: def test_json_serialization_user_config(serve_instance):
      """See https://github.com/ray-project/ray/issues/25345.
  
      See https://github.com/ray-project/ray/pull/26235 for additional context
      about this test.
      """
  
      @serve.deployment(name="simple-deployment")
      class SimpleDeployment:
          value: str
          nested_value: str
  
          def reconfigure(self, config: Dict) -> None:
              self.value = config["value"]
              self.nested_value = config["nested"]["value"]
  
          def get_value(self) -> None:
              return self.value
  
          def get_nested_value(self) -> None:
              return self.nested_value
  
      app = SimpleDeployment.options(
          user_config={
              "value": "Success!",
              "nested": {"value": "Success!"},
          }
      ).bind()
      handle = serve.run(app)
  
      assert handle.get_value.remote().result() == "Success!"
      assert handle.get_nested_value.remote().result() == "Success!"
  
      handle = serve.run(
          SimpleDeployment.options(
              user_config={
                  "value": "Failure!",
                  "another-value": "Failure!",
                  "nested": {"value": "Success!"},
              }
          ).bind()
      )
  
      assert handle.get_value.remote().result() == "Failure!"
      assert handle.get_nested_value.remote().result() == "Success!"
  
imports: import functools
  import os
  import sys
  import threading
  import time
  from concurrent.futures.thread import ThreadPoolExecutor
  from typing import Dict
  import pytest
  import requests
  import ray
  from ray import serve
  from ray._private.pydantic_compat import ValidationError
  from ray._private.test_utils import SignalActor, wait_for_condition
  from ray.serve._private.common import ApplicationStatus
  from ray.serve._private.logging_utils import get_component_log_file_name, get_serve_logs_dir
  from ray.util.state import list_actors
label_desc: Use image node_id 4 for calling a global function with example usage: test_json_serialization_user_config(serve_instance) and returns: self, self