Display a message in lbl_feedback, which times out after some
        number of seconds.

def _show_feedback_label(self, message, seconds=None):
        """Display a message in lbl_feedback, which times out after some
        number of seconds.
        """
        if seconds is None:
            seconds = CONFIG['MESSAGE_DURATION']

        logger.debug('Label feedback: "{}"'.format(message))

        self.feedback_label_timer.timeout.connect(self._hide_feedback_label)
        self.lbl_feedback.setText(str(message))
        self.lbl_feedback.show()
        self.feedback_label_timer.start(1000 * seconds)