@Override public ImSortedSet<E> subSet(E fromElement, E toElement) {
        return PersistentTreeSet.ofMap(impl.subMap(fromElement, toElement));
    }
@Override public ImSortedSet<E> subSet(E fromElement, E toElement) {
        return PersistentTreeSet.ofMap(impl.subMap(fromElement, toElement));
    }
@ Override public ImSortedSet < E > subSet ( E fromElement , E toElement ) { return PersistentTreeSet . ofMap ( impl . subMap ( fromElement , toElement ) ) ; }
{@inheritDoc}
{