code: def set_headline(self, level, message, timestamp=None, now_reference=None):
          
  
          if self.headline is not None and self.headline.message == message:
              self.headline.created = monotonic()
              self.headline.count += 1
              return
  
          msg_object = ServiceMessage(level, message, self._last_message_id, timestamp, now_reference)
          self.headline = msg_object
          self._last_message_id += 1
docs: Set the persistent headline message for this service.
  
          Args:
              level (int): The level of the message (info, warning, error)
              message (string): The message contents
              timestamp (float): An optional monotonic value in seconds for when the message was created
              now_reference (float): If timestamp is not relative to monotonic() as called from this
                  module then this should be now() as seen by whoever created the timestamp.