private void addFeatureIterators(PredicateQuery query, FeatureIndex featureIndex, List<ConjunctionIdIterator> iterators) {
            query.getFeatures().stream()
                    .map(e -> toSingleTermIterator(e, featureIndex))
                    .filter(Optional::isPresent)
                    .map(Optional::get)
                    .forEach(iterators::add);
        }
Retrieves a list of hits for the given query.

@param query Specifies the boolean variables that are true.
@return List of hits
predicate-search/src/main/java/com/yahoo/search/predicate/index/conjunction/ConjunctionIndex.java