@Override
public Set<String> addInPlace(final Set<String> r, final Set<String> t) {
r.addAll(t);
return r;
}
@Override
public Set<String> addAccumulator(final Set<String> r, final Set<String> t) {
Set<String> rx = new HashSet<String>(r);
rx.addAll(t);
return rx;
}