private Hit getMatchingFilledHit(URI hitToFillId, Result filledHits) {
        Hit filledHit = null;

        for (Hit filledHitCandidate : filledHits.hits()) {
            if ( hitToFillId == filledHitCandidate.getId() ) {
                filledHit = filledHitCandidate;
                break;
            }
        }
        return filledHit;
    }
Returns a query clone which has sourcr, offset and hits set to null. This is used by access to
the maps using the query as key to achieve lookup independent of offset/hits value
container-search/src/main/java/com/yahoo/search/searchchain/testutil/DocumentSourceSearcher.java