code: def test_simple_single_class(serve_instance):
      ray_dag = Model.bind(2, ratio=0.3)
  
      with _DAGNodeNameGenerator() as node_name_generator:
          serve_root_dag = ray_dag.apply_recursive(
              lambda node: transform_ray_dag_to_serve_dag(
                  node, node_name_generator, ""
              )
          )
      deployments = extract_deployments_from_serve_dag(serve_root_dag)
      assert len(deployments) == 1
      deployments[0]._deploy()
      _validate_consistent_python_output(
          deployments[0], ray_dag, "Model", input=1, output=0.6
      )
  
file_path: ray/python/ray/serve/tests/test_deployment_graph_build.py
imports: import pytest
  import requests
  import ray
  from ray import serve
  from ray.dag.utils import _DAGNodeNameGenerator
  from ray.serve._private import api
  from ray.serve._private.deployment_graph_build import extract_deployments_from_serve_dag, transform_ray_dag_to_serve_dag
  from ray.serve.handle import DeploymentHandle
  from ray.serve.tests.common.test_modules import NESTED_HANDLE_KEY, Combine, Model
label_desc: Use image node_id 3 for calling a global function with example usage: test_simple_single_class(serve_instance) without return types