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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 date_to_number(self, date):
 """ Converts a date or datetime instance to a corresponding float value. """

        if isinstance(date, datetime.datetime):
            delta = date - self._null_date
        elif isinstance(date, datetime.date):
            delta = date - self._null_date.date()
        else:
            raise TypeError(date)
        return delta.days + delta.seconds / (24.0 * 60 * 60)