private static void incrementOccurrence(Map<Long, Integer> featureOccurrences, long featureHash) {
        featureOccurrences.merge(featureHash, 1, Integer::sum);
    }
@param predicate The predicate tree.
@return a result object containing the min-feature value, the tree size and sub-tree sizes.
predicate-search/src/main/java/com/yahoo/search/predicate/annotator/PredicateTreeAnalyzer.java