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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 terminating_sip_domains(self):
 """ Access the terminating_sip_domains :returns: twilio.rest.trunking.v1.trunk.terminating_sip_domain.TerminatingSipDomainList :rtype: twilio.rest.trunking.v1.trunk.terminating_sip_domain.TerminatingSipDomainList """

        if self._terminating_sip_domains is None:
            self._terminating_sip_domains = TerminatingSipDomainList(
                self._version,
                trunk_sid=self._solution['sid'],
            )
        return self._terminating_sip_domains