return (Multiset<E>) delegate;
    }

    @LazyInit @CheckForNull transient Set<E> elementSet;

    Set<E> createElementSet() {
      return Collections.<E>unmodifiableSet(delegate.elementSet());
    }

    @Override
    public Set<E> elementSet() {
      Set<E> es = elementSet;
      return (es == null) ? elementSet = createElementSet() : es;
    }

  public static <E extends Comparable<? super E>> ImmutableSortedMultiset<E> of(E element) {
    RegularImmutableSortedSet<E> elementSet =
        (RegularImmutableSortedSet<E>) ImmutableSortedSet.of(element);
    long[] cumulativeCounts = {0, 1};
    return new RegularImmutableSortedMultiset<>(elementSet, cumulativeCounts, 0, 1);
  }

  /**

  @Override
  public String toString() {
    return entrySet().toString();
  }

  /** @since 21.0 (present with return type {@code Set} since 2.0) */
  @Override
  public abstract ImmutableSet<E> elementSet();

  @LazyInit @CheckForNull private transient ImmutableSet<Entry<E>> entrySet;

  @Override
  public ImmutableSet<Entry<E>> entrySet() {
    ImmutableSet<Entry<E>> es = entrySet;

  }

  static boolean removeAllImpl(Set<?> set, Collection<?> collection) {
    checkNotNull(collection); // for GWT
    if (collection instanceof Multiset) {
      collection = ((Multiset<?>) collection).elementSet();
    }
    /*
     * AbstractSet.removeAll(List) has quadratic behavior if the list size
     * is just more than the set's size.  We augment the test by

        }
      }
      return oldCount;
    }

    @Override
    public void clear() {
      multimap.clear();
    }

    @Override
    public Set<K> elementSet() {
      return multimap.keySet();
    }

    @Override
    Iterator<K> elementIterator() {
      throw new AssertionError("should never be called");
    }
  }