code: def list_subdomains_previous_page(self):
          
          uri = self._paging.get("subdomain", {}).get("prev_uri")
          if uri is None:
              raise exc.NoMoreResults("There are no previous pages of subdomains "
                      "to list.")
          return self._list_subdomains(uri)
docs: When paging through subdomain results, this will return the previous
          page, using the same limit. If there are no more results, a
          NoMoreResults exception will be raised.