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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 async def stop(self):
 """ Irreversibly stop the sender. """

        if self.__started:
            self.__transport._unregister_rtp_sender(self)
            self.__rtp_task.cancel()
            self.__rtcp_task.cancel()
            await asyncio.gather(
                self.__rtp_exited.wait(),
                self.__rtcp_exited.wait())