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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 delete_arrays(self, period = None):
 """ If ``period`` is ``None``, remove all known values of the variable. If ``period`` is not ``None``, only remove all values for any period included in period (e.g. if period is "2017", values for "2017-01", "2017-07", etc. would be removed) """


        self._memory_storage.delete(period)
        if self._disk_storage:
            self._disk_storage.delete(period)