def log_proto(self, message, **kw):
        """Add a protobuf entry to be logged during :meth:`commit`.

        :type message: protobuf message
        :param message: the protobuf entry

        :type kw: dict
        :param kw: (optional) additional keyword arguments for the entry.
                   See :class:`~google.cloud.logging.entries.LogEntry`.
        """
        self.entries.append(ProtobufEntry(payload=message, **kw))