grpc_session_attr_release_np
    - frees memory for the session attribute value.
  grpc_error_t grpc_session_attr_release_np(void *value)
  void *valueThe grpc_session_attr_release_np() frees memory for the value obtained by grpc_session_attr_get_np().
This function is MT-safe.
If successful, GRPC_NO_ERROR is returned. In the case of an error, an error code is returned.
  GRPC_NOT_INITIALIZED  GRPC_OTHER_ERROR_CODE