docs: public synchronized List<ACL> convertLong(Long longVal) {
          if (longVal == null)
              return null;
          if (longVal == -1L)
              return Ids.OPEN_ACL_UNSAFE;
          List<ACL> acls = longKeyMap.get(longVal);
          if (acls == null) {
              LOG.error("ERROR: ACL not available for long " + longVal);
              throw new RuntimeException("Failed to fetch acls for " + longVal);
          }
          return acls;
      }