@Override
  public int count(@Nullable Object element) {
    return forward.count(element);
  }

  @Override
  public @Nullable Entry<E> firstEntry() {
    return forward.lastEntry();
  }

  @Override
  public @Nullable Entry<E> lastEntry() {
    return forward.firstEntry();
  }

  @Override
  public int size() {
    return forward.size();
  }

  @Override
  public ImmutableSortedSet<E> elementSet() {

    return new SortedMultisets.ElementSet<E>(this);
  }

  @Override
  public Comparator<? super E> comparator() {
    return comparator;
  }

  @Override
  public @Nullable Entry<E> firstEntry() {
    Iterator<Entry<E>> entryIterator = entryIterator();
    return entryIterator.hasNext() ? entryIterator.next() : null;
  }

  @Override
  public @Nullable Entry<E> lastEntry() {

    valueIterator.next();
    valueIterator.remove();
    assertFalse(underlying.containsKey("e"));

    Set<Entry<String, String>> entries = map.entrySet();
    Entry<String, String> firstEntry = entries.iterator().next();
    entries.remove(firstEntry);
    assertFalse(underlying.containsKey("f"));

    Iterator<Entry<String, String>> entryIterator = entries.iterator();
    entryIterator.next();
    entryIterator.remove();

    return new SortedMultisets.NavigableElementSet<>(this);
  }

  @Override
  public Comparator<? super E> comparator() {
    return comparator;
  }

  @Override
  public @Nullable Entry<E> firstEntry() {
    Iterator<Entry<E>> entryIterator = entryIterator();
    return entryIterator.hasNext() ? entryIterator.next() : null;
  }

  @Override
  public @Nullable Entry<E> lastEntry() {

    checkNotNull(action);
    for (int i = 0; i < length; i++) {
      action.accept(elementSet.asList().get(i), getCount(i));
    }
  }

  @Override
  public @Nullable Entry<E> firstEntry() {
    return isEmpty() ? null : getEntry(0);
  }

  @Override
  public @Nullable Entry<E> lastEntry() {
    return isEmpty() ? null : getEntry(length - 1);
  }

  @Override

    return new SortedMultisets.NavigableElementSet<>(this);
  }

  @Override
  public Comparator<? super E> comparator() {
    return comparator;
  }

  @Override
  public @Nullable Entry<E> firstEntry() {
    Iterator<Entry<E>> entryIterator = entryIterator();
    return entryIterator.hasNext() ? entryIterator.next() : null;
  }

  @Override
  public @Nullable Entry<E> lastEntry() {

    valueIterator.next();
    valueIterator.remove();
    assertFalse(underlying.containsKey("e"));

    Set<Entry<String, String>> entries = map.entrySet();
    Entry<String, String> firstEntry = entries.iterator().next();
    entries.remove(firstEntry);
    assertFalse(underlying.containsKey("f"));

    Iterator<Entry<String, String>> entryIterator = entries.iterator();
    entryIterator.next();
    entryIterator.remove();

  }

  @Override
  public Range<K> span() {
    Entry<Cut<K>, RangeMapEntry<K, V>> firstEntry = entriesByLowerBound.firstEntry();
    Entry<Cut<K>, RangeMapEntry<K, V>> lastEntry = entriesByLowerBound.lastEntry();
    // Either both are null or neither is, but we check both to satisfy the nullness checker.
    if (firstEntry == null || lastEntry == null) {
      throw new NoSuchElementException();
    }
    return Range.create(

   */
  @Override
  Comparator<? super E> comparator();

  /**
   * Returns the entry of the first element in this multiset, or {@code null} if this multiset is
   * empty.
   */
  @Nullable Entry<E> firstEntry();

  /**
   * Returns the entry of the last element in this multiset, or {@code null} if this multiset is
   * empty.
   */
  @Nullable Entry<E> lastEntry();

  /**

   */
  @Override
  Comparator<? super E> comparator();

  /**
   * Returns the entry of the first element in this multiset, or {@code null} if this multiset is
   * empty.
   */
  @Nullable Entry<E> firstEntry();

  /**
   * Returns the entry of the last element in this multiset, or {@code null} if this multiset is
   * empty.
   */
  @Nullable Entry<E> lastEntry();

  /**