HitList newHitList(int listIdx, int tag, HitsAggregationResult execResult) {
            HitList hitList = new HitList(transform.getLabel(tag));
            List<Hit> hits = execResult.getHits();
            PageInfo page = new PageInfo(resultId.newChildId(listIdx), tag, stable, hits.size());
            for (int i = page.firstEntry; i < page.lastEntry; ++i) {
                hitList.add(hitConverter.toSearchHit(execResult.getSummaryClass(), hits.get(i)));
            }
            page.putContinuations(hitList.continuations());
            return hitList;
        }
Constructs the grouping result tree that corresponds to the parameters given to this builder. This method might
fail due to unsupported constructs in the results, in which case an exception is thrown.

@throws IllegalInputException Thrown if the grouping result contains unsupported constructs.
container-search/src/main/java/com/yahoo/search/grouping/vespa/ResultBuilder.java