code: def parse_watermark_notification(p):
      
      return WatermarkNotification(
          conv_id=p.conversation_id.id,
          user_id=from_participantid(p.sender_id),
          read_timestamp=from_timestamp(
              p.latest_read_timestamp
          ),
      )
docs: Return WatermarkNotification from hangouts_pb2.WatermarkNotification.