code: def domains(self):
          
          if self._domains is None:
              self._domains = DomainList(self._version, account_sid=self._solution['account_sid'], )
          return self._domains
docs: Access the domains
  
          :returns: twilio.rest.api.v2010.account.sip.domain.DomainList
          :rtype: twilio.rest.api.v2010.account.sip.domain.DomainList