grpc_call_with_attr_np - Executes an RPC.
  grpc_error_t grpc_call_with_attr_np(grpc_function_handle_t *handle, grpc_session_attr_t_np *session_attr, ...)
  grpc_function_handle_t *handle  grpc_session_attr_t_np *session_attr  Other argumentsThe grpc_call_with_attr_np() function calls the function defined by the function handle. The grpc_call_with_attr_np() function is blocked until the called function completes execution.
This function is MT-safe.
If successful, GRPC_NO_ERROR is returned. In the case of an error, Error code is returned.
  GRPC_NOT_INITIALIZED  GRPC_SERVER_NOT_FOUND  GRPC_FUNCTION_NOT_FOUND  GRPC_INVALID_FUNCTION_HANDLE  GRPC_RPC_REFUSED  GRPC_COMMUNICATION_FAILED  GRPC_TIMEOUT_NP  GRPC_OTHER_ERROR_CODE