<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 async def on_unknown(self, message):
 """ Unknown command. """

        self.logger.warning('Unknown command: [%s] %s %s', message.source, message.command,
                            message.params)