@Override
        public boolean equals(Object o) {
            if (!(o instanceof MissingValueSettings other)) return false;
            if (missingPolicy != other.missingPolicy) return false;
            if (missingValue == null) {
                return other.missingValue == null;
            }
            if (other.missingValue == null) return false;
            return missingValue.equals(other.missingValue);
        }
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