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