}

  @Override
  public NavigableSet<E> headSet(@ParametricNullness E toElement, boolean inclusive) {
    return delegate().headSet(toElement, inclusive);
  }

  /**
   * A sensible definition of {@link #headSet(Object)} in terms of the {@link #headSet(Object,
   * boolean)} method. If you override {@link #headSet(Object, boolean)}, you may wish to override
   * {@link #headSet(Object)} to forward to this implementation.
   */

  }

  @Override
  public NavigableSet<E> headSet(@ParametricNullness E toElement, boolean inclusive) {
    return delegate().headSet(toElement, inclusive);
  }

  /**
   * A sensible definition of {@link #headSet(Object)} in terms of the {@link #headSet(Object,
   * boolean)} method. If you override {@link #headSet(Object, boolean)}, you may wish to override
   * {@link #headSet(Object)} to forward to this implementation.
   */

    return delegate().comparator();
  }

  @Override
  @ParametricNullness
  public E first() {
    return delegate().first();
  }

  @Override
  public SortedSet<E> headSet(@ParametricNullness E toElement) {
    return delegate().headSet(toElement);
  }

  @Override
  @ParametricNullness
  public E last() {
    return delegate().last();
  }

  @Override

      return multiset().subMultiset(fromElement, CLOSED, toElement, OPEN).elementSet();
    }

    @Override
    public SortedSet<E> headSet(@ParametricNullness E toElement) {
      return multiset().headMultiset(toElement, OPEN).elementSet();
    }

    @Override
    public SortedSet<E> tailSet(@ParametricNullness E fromElement) {

    super(Ordering.natural());
    this.domain = domain;
  }

  @Override
  public ContiguousSet<C> headSet(C toElement) {
    return headSetImpl(checkNotNull(toElement), false);
  }

  /**
   * @since 12.0
   */
  @GwtIncompatible // NavigableSet
  @Override
  public ContiguousSet<C> headSet(C toElement, boolean inclusive) {
    return headSetImpl(checkNotNull(toElement), inclusive);
  }

    return delegate().comparator();
  }

  @Override
  @ParametricNullness
  public E first() {
    return delegate().first();
  }

  @Override
  public SortedSet<E> headSet(@ParametricNullness E toElement) {
    return delegate().headSet(toElement);
  }

  @Override
  @ParametricNullness
  public E last() {
    return delegate().last();
  }

  @Override

  public @Nullable E floor(E e) {
    return delegate.floor(checkValid(e));
  }

  @Override
  public SortedSet<E> headSet(E toElement) {
    return headSet(toElement, false);
  }

  @Override
  public NavigableSet<E> headSet(E toElement, boolean inclusive) {
    return new SafeTreeSet<>(delegate.headSet(checkValid(toElement), inclusive));
  }

  @Override
  public @Nullable E higher(E e) {

  public @Nullable E floor(E e) {
    return delegate.floor(checkValid(e));
  }

  @Override
  public SortedSet<E> headSet(E toElement) {
    return headSet(toElement, false);
  }

  @Override
  public NavigableSet<E> headSet(E toElement, boolean inclusive) {
    return new SafeTreeSet<>(delegate.headSet(checkValid(toElement), inclusive));
  }

  @Override
  public @Nullable E higher(E e) {

    ImmutableSortedSet<E> set = headSet(e, true);
    return !set.isEmpty() ? set.last() : null;
  }

  public ImmutableSortedSet<E> headSet(E toElement, boolean inclusive) {
    checkNotNull(toElement);
    if (inclusive) {
      E tmp = higher(toElement);
      if (tmp == null) {
        return this;
      }
      toElement = tmp;
    }
    return headSet(toElement);
  }

  @Override

      return multiset().subMultiset(fromElement, CLOSED, toElement, OPEN).elementSet();
    }

    @Override
    public SortedSet<E> headSet(@ParametricNullness E toElement) {
      return multiset().headMultiset(toElement, OPEN).elementSet();
    }

    @Override
    public SortedSet<E> tailSet(@ParametricNullness E fromElement) {