<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def publish_if_new(cls):
 """If the station map has changed, publish the new information."""

    message = cls.make_message()
    if message != cls.last_message:
      super(DashboardPubSub, cls).publish(message)
      cls.last_message = message