@SuppressWarnings({ "rawtypes", "unchecked" })
        public int compare(Comparable a, Comparable b) {
            if ((a instanceof String) && (b instanceof String)) {
                return ((String)a).compareToIgnoreCase((String) b);
            }
            return a.compareTo(b);
        }
Returns the serial form of this which contains all information needed to reconstruct this sorter
container-search/src/main/java/com/yahoo/search/query/Sorting.java