@SuppressWarnings({ "rawtypes", "unchecked" })
        @Override
        public int compare(Entry<Object, Integer> o1, Entry<Object, Integer> o2) {
            Comparable c1 = (Comparable) o1.getKey();
            Comparable c2 = (Comparable) o2.getKey();
            return c1.compareTo(c2);
        }
Serialize Vespa query trees to YQL+ strings.

@author Steinar Knutsen
container-search/src/main/java/com/yahoo/search/yql/VespaSerializer.java