@Override
        public AttributeSorter clone() {
            try {
                return (AttributeSorter)super.clone();
            }
            catch (CloneNotSupportedException e) {
                throw new RuntimeException(e);
            }

        }
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