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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 days(self):
 """ Access the days :returns: twilio.rest.preview.bulk_exports.export.day.DayList :rtype: twilio.rest.preview.bulk_exports.export.day.DayList """

        if self._days is None:
            self._days = DayList(self._version, resource_type=self._solution['resource_type'], )
        return self._days