* each key, use {@link #keySet}.
   */
  @Override
  public ImmutableMultiset<K> keys() {
    return (ImmutableMultiset<K>) super.keys();
  }

  @Override
  ImmutableMultiset<K> createKeys() {
    return new Keys();
  }

  @SuppressWarnings("serial") // Uses writeReplace, not default serialization
  @WeakOuter
  private final class Keys extends ImmutableMultiset<K> {
    @Override

   * each key, use {@link #keySet}.
   */
  @Override
  public ImmutableMultiset<K> keys() {
    return (ImmutableMultiset<K>) super.keys();
  }

  @Override
  ImmutableMultiset<K> createKeys() {
    return new Keys();
  }

  @SuppressWarnings("serial") // Uses writeReplace, not default serialization
  @WeakOuter
  private final class Keys extends ImmutableMultiset<K> {
    @Override

   * classes like LinkedHashMultimap that need to say something different are
   * still able to {@inheritDoc} all the way from Multimap?
   */

  @Override
  Multiset<K> createKeys() {
    return new Multimaps.Keys<K, V>(this);
  }

  /**
   * {@inheritDoc}
   *
   * <p>The iterator generated by the returned collection traverses the values for one key, followed