private HitGroup createAggregationGroup(String label) {
            Group root = new Group(new RootId(0), new Relevance(1));
            GroupList groupList = new GroupList(label);
            root.add(groupList);
            Group value = new Group(new LongId(37L), new Relevance(2.11));
            groupList.add(value);
            return root;
        }
Simulates the return when grouping is used for aggregation purposes and there is a plain hit list in addition:
The returned result contains both regular hits at the top level (from non-grouping)
and groups contained aggregation information.
container-search/src/test/java/com/yahoo/prelude/searcher/test/FieldCollapsingSearcherTestCase.java