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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 start_periodic_snapshots(self, interval=1.0):
 """ Start a thread which takes snapshots periodically. The `interval` specifies the time in seconds the thread waits between taking snapshots. The thread is started as a daemon allowing the program to exit. If periodic snapshots are already active, the interval is updated. """

        if not self._periodic_thread:
            self._periodic_thread = PeriodicThread(self, interval, name='BackgroundMonitor')
            self._periodic_thread.setDaemon(True)
            self._periodic_thread.start()
        else:
            self._periodic_thread.interval = interval