public void traverse(ObjectTraverser ot) {
            for (int i = 0; i < hashlet.size(); i++) {
                String fn = hashlet.key(i);
                int offset = hashlet.value(i);
                ot.field(fn, valueAt(offset));
            }
        }
MatchFeatureData helps pack match features for hits into
inspectable HitValue objects, all sharing the same Hashlet
for the field names.

@author arnej
vespajlib/src/main/java/com/yahoo/data/access/helpers/MatchFeatureData.java