code: def registrations(self):
          
          if self._registrations is None:
              self._registrations = AuthTypeRegistrationsList(
                  self._version,
                  account_sid=self._solution['account_sid'],
                  domain_sid=self._solution['domain_sid'],
              )
          return self._registrations
docs: Access the registrations
  
          :returns: twilio.rest.api.v2010.account.sip.domain.auth_types.auth_registrations_mapping.AuthTypeRegistrationsList
          :rtype: twilio.rest.api.v2010.account.sip.domain.auth_types.auth_registrations_mapping.AuthTypeRegistrationsList