private static void addFeatures(FeatureSet featureSet, Set<Long> features) {
        String key = featureSet.getKey();
        featureSet.getValues().forEach(value -> features.add(Feature.createHash(key, value)));
    }
K value - number of non-negated operands
predicate-search/src/main/java/com/yahoo/search/predicate/index/conjunction/IndexableFeatureConjunction.java