grpc_session_attr_get_np - Gets handle attributes.
  grpc_error_t grpc_session_attr_get_np(grpc_session_attr_t_np *attr,
                                grpc_session_attr_name_t_np name,
                                void **value)
  grpc_session_attr_t_np *attr  grpc_session_attr_name_t_np name  void *valueMemory area allocated for the attribute value should be released by calling grpc_session_attr_release_np() after the value was referred.
This function is MT-safe.
  GRPC_NOT_INITIALIZED  GRPC_OTHER_ERROR_CODE