code: def __call__(self, *args):
      return self._message
  
file_path: ray/python/ray/serve/tests/test_config_files/arg_builders.py
imports: from ray import serve
  from ray._private.pydantic_compat import BaseModel
label_desc: Use image node_id 2 for calling the Echo obj's underlying member method code with example usage: obj.__call__() and returns: self