docs: public RollupInterval getRollupInterval(final String interval) {
      if (interval == null || interval.isEmpty()) {
        throw new IllegalArgumentException("Interval cannot be null or empty");
      }
      final RollupInterval rollup = forward_intervals.get(interval);
      if (rollup == null) {
        throw new NoSuchRollupForIntervalException(interval);
      }
      return rollup;
    }