code: def dflt_interval(self, cd_id: str) -> (int, int):
          LOGGER.debug('RevocationCache.dflt_interval >>>')
          fro = None
          to = None
          for rr_id in self:
              if cd_id != rev_reg_id2cred_def_id(rr_id):
                  continue
              entry = self[rr_id]
              if entry.rr_delta_frames:
                  to = max(entry.rr_delta_frames, key=lambda f: f.to).to
                  fro = min(fro or to, to)
          if not (fro and to):
              LOGGER.debug(
                  'RevocationCache.dflt_interval <!< No data for default non-revoc interval on cred def id %s',
                  cd_id)
              raise CacheIndex('No data for default non-revoc interval on cred def id {}'.format(cd_id))
          rv = (fro, to)
          LOGGER.debug('RevocationCache.dflt_interval <<< %s', rv)
          return rv