@Override
        public Collection<IntegerFieldValue> values() {
            Collection<IntegerFieldValue> ret = new ArrayList<>();
            for (Object v : map.values()) {
                ret.add(wrapValue(v));
            }
            return ret;
        }
Weighted set MapFieldValue, backed by map of native Java types.
Note: The key type of this is FieldValue, not K.
@author vegardh
document/src/main/java/com/yahoo/document/datatypes/WeightedSet.java