class KeywordsCombiner implements BinaryOperator<Keywords> {

    @Override
    public Keywords apply(Keywords keywords, Keywords keywords2) {
        return keywordsFactory
            .fromSet(Sets.union(
                        union(keywords.getKeywords(), keywords2.getKeywords(), KEYWORD_NOT_TO_UNION),
                        intersect(keywords.getKeywords(), keywords2.getKeywords(), KEYWORD_TO_INTERSECT)));
    }

    public  KeywordsCombiner();

}