code: def __call__(self, m1_output, m2_output, kwargs_output=0):
      return m1_output + m2_output + kwargs_output
  
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 1 for calling the Add obj's underlying member method code with example usage: obj.__call__(m1_output, m2_output, kwargs_output) and returns: unknown