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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):
 """Stop this task and wait until it and all its subtasks end. This function will finalize this task either by using the finalizer function passed during creation or by calling task.cancel() if no finalizer was passed. It will then call join() on this task and any registered subtasks with the given maximum timeout, raising asyncio.TimeoutError if the tasks did not exit within the given timeout. This method should only be called once. After this method returns, the task is finished and no more subtasks can be added. If this task is being tracked inside of the BackgroundEventLoop that it is part of, it will automatically be removed from the event loop's list of tasks. """


        if self.stopped:
            return

        self._logger.debug("Stopping task %s", self.name)

        if self._finalizer is not None:
            try:
                result = self._finalizer(self)
                if inspect.isawaitable(result):
                    await result
            except:  #pylint:disable=bare-except;We need to make sure we always wait for the task
                self._logger.exception("Error running finalizer for task %s",
                                       self.name)
        elif self.task is not None:
            self.task.cancel()

        tasks = []
        if self.task is not None:
            tasks.append(self.task)

        tasks.extend(x.task for x in self.subtasks)
        finished = asyncio.gather(*tasks, return_exceptions=True)
        outcomes = []

        try:
            outcomes = await asyncio.wait_for(finished, timeout=self._stop_timeout)
        except asyncio.TimeoutError as err:
            # See discussion here: https://github.com/python/asyncio/issues/253#issuecomment-120138132
            # This prevents a nuisance log error message, finished is guaranteed
            # to be cancelled but not awaited when wait_for() has a timeout.
            try:
                outcomes = await finished
            except asyncio.CancelledError:
                pass

            # See https://mail.python.org/pipermail/python-3000/2008-May/013740.html
            # for why we need to explictly name the error here
            raise err
        finally:
            self.stopped = True
            for outcome in outcomes:
                if isinstance(outcome, Exception) and not isinstance(outcome, asyncio.CancelledError):
                    self._logger.error(outcome)

            if self in self._loop.tasks:
                self._loop.tasks.remove(self)