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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 usage_records(self):
 """ Access the usage_records :returns: twilio.rest.wireless.v1.sim.usage_record.UsageRecordList :rtype: twilio.rest.wireless.v1.sim.usage_record.UsageRecordList """

        if self._usage_records is None:
            self._usage_records = UsageRecordList(self._version, sim_sid=self._solution['sid'], )
        return self._usage_records