public void addFeature(String key, String value, long subqueryBitMap) {
        features.add(new Feature(key, value, subqueryBitMap));
    }
Adds a feature to the query, e.g. gender = male.

@param key Feature key
@param value Feature value
@param subqueryBitMap The subquery bitmap for which this term is true
predicate-search/src/main/java/com/yahoo/search/predicate/PredicateQuery.java