<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 stop(self):
 """ Irreversibly stop the receiver. """

        if self.__started:
            self.__transport._unregister_rtp_receiver(self)
            self.__stop_decoder()
            self.__rtcp_task.cancel()
            await self.__rtcp_exited.wait()