message: Add a method_name and a tf.saved_model.save
  Previously method_name was blank. We'll never be able to set "classify" or "regress", so everything will be predict.
  I will follow up with a tensorflow_serving integration test (in that repo) due to sync issues.
  Fixes
diff: @@ -479,7 +479,8 @@ def _generate_signatures(signature_functions, resource_map):
  function.name, signature_key)
  signatures[signature_key] = signature_def_utils.build_signature_def(
  _tensor_dict_to_tensorinfo(exterior_argument_placeholders),
  - _tensor_dict_to_tensorinfo(outputs))
  + _tensor_dict_to_tensorinfo(outputs),
  + method_name=signature_constants.PREDICT_METHOD_NAME)
  return signatures
  