docs: def send_notification(self, subject="", message="", sender="", source=None, actions=None):
          """
          Sends a notification. Blocks as long as necessary.
  
          :param subject: The subject.
          :type subject: str
          :param message: The message.
          :type message: str
          :param sender: The sender.
          :type sender: str
          :param source: The source of the notification
          :type source: .LegacyNotification.Source
          :param actions Actions to be sent with a notification (list of TimelineAction objects)
          :type actions list
          """
          if self._pebble.firmware_version.major < 3:
              self._send_legacy_notification(subject, message, sender, source)
          else:
              self._send_modern_notification(subject, message, sender, source, actions)