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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:
 def stop(self):
 """Stop the background thread."""

        self._stop_event.set()
        if not self.persistence:
            return
        if self._cancel_save is not None:
            self._cancel_save()
            self._cancel_save = None
        self.persistence.save_sensors()