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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 verifications(self):
 """ Access the verifications :returns: twilio.rest.preview.acc_security.service.verification.VerificationList :rtype: twilio.rest.preview.acc_security.service.verification.VerificationList """

        if self._verifications is None:
            self._verifications = VerificationList(self._version, service_sid=self._solution['sid'], )
        return self._verifications