}

  @Override
  abstract SortedSet<V> createCollection();

  @Override
  SortedSet<V> createUnmodifiableEmptyCollection() {
    return unmodifiableCollectionSubclass(createCollection());
  }

  @Override
  <E extends @Nullable Object> SortedSet<E> unmodifiableCollectionSubclass(
      Collection<E> collection) {
    if (collection instanceof NavigableSet) {
      return unmodifiableNavigableSet((NavigableSet<E>) collection);

  @Override
  abstract Set<V> createCollection();

  @Override
  Set<V> createUnmodifiableEmptyCollection() {
    return emptySet();
  }

  @Override
  <E extends @Nullable Object> Collection<E> unmodifiableCollectionSubclass(
      Collection<E> collection) {
    return unmodifiableSet((Set<E>) collection);
  }

  @Override
  Collection<V> wrapCollection(@ParametricNullness K key, Collection<V> collection) {

  @Override
  abstract Set<V> createCollection();

  @Override
  Set<V> createUnmodifiableEmptyCollection() {
    return emptySet();
  }

  @Override
  <E extends @Nullable Object> Collection<E> unmodifiableCollectionSubclass(
      Collection<E> collection) {
    return unmodifiableSet((Set<E>) collection);
  }

  @Override
  Collection<V> wrapCollection(@ParametricNullness K key, Collection<V> collection) {

    }

    @Override
    protected Collection<V> createCollection() {
      return factory.get();
    }

    @Override
    <E extends @Nullable Object> Collection<E> unmodifiableCollectionSubclass(
        Collection<E> collection) {
      if (collection instanceof NavigableSet) {
        return Sets.unmodifiableNavigableSet((NavigableSet<E>) collection);
      } else if (collection instanceof SortedSet) {