}

  @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 Sets.unmodifiableNavigableSet((NavigableSet<E>) collection);

  }

  @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 Sets.unmodifiableNavigableSet((NavigableSet<E>) collection);

  abstract List<V> createCollection();

  @Override
  List<V> createUnmodifiableEmptyCollection() {
    return Collections.emptyList();
  }

  @Override
  <E extends @Nullable Object> Collection<E> unmodifiableCollectionSubclass(
      Collection<E> collection) {
    return Collections.unmodifiableList((List<E>) collection);
  }

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

  abstract Set<V> createCollection();

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

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

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

  abstract Set<V> createCollection();

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

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

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

  abstract List<V> createCollection();

  @Override
  List<V> createUnmodifiableEmptyCollection() {
    return Collections.emptyList();
  }

  @Override
  <E extends @Nullable Object> Collection<E> unmodifiableCollectionSubclass(
      Collection<E> collection) {
    return Collections.unmodifiableList((List<E>) collection);
  }

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