* @return A PopularWordsResponse instance.
     */
    protected PopularWordsResponse createResponse(final SearchResponse searchResponse) {
        final SearchHit[] hits = searchResponse.getHits().getHits();
        final List<String> words = new ArrayList<>();
        final List<SuggestItem> items = new ArrayList<>();

        final String index;
        if (hits.length > 0) {

                .setSize(fessConfig.getPageScoreBoosterMaxFetchSizeAsInteger())
                .execute()
                .actionGet(requestTimeout);
        return Arrays.stream(response.getHits().getHits()).map(SearchHit::getId).toArray(n -> new String[n]);
    };

    /**
     * A function to handle requests.
     */
    protected Function<Map<String, Object>, Long> requestHandler = params -> {