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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 _past_datetime_from(self):
 """ The datetime this event previously started in the local time zone, or None if it never did. """

        prevDt = self.__localBefore(timezone.localtime(), dt.time.max,
                                    excludeCancellations=True,
                                    excludeExtraInfo=True)
        return prevDt