private static final long serialVersionUID = 0;
  }

  static <E extends @Nullable Object> Multiset<E> multiset(
      Multiset<E> multiset, @CheckForNull Object mutex) {
    if (multiset instanceof SynchronizedMultiset || multiset instanceof ImmutableMultiset) {
      return multiset;
    }
    return new SynchronizedMultiset<>(multiset, mutex);
  }

  static final class SynchronizedMultiset<E extends @Nullable Object>

    }

    @Override
    Iterator<Multiset.Entry<K>> entryIterator() {
      return new TransformedIterator<Map.Entry<K, Collection<V>>, Multiset.Entry<K>>(
          multimap.asMap().entrySet().iterator()) {
        @Override
        Multiset.Entry<K> transform(final Map.Entry<K, Collection<V>> backingEntry) {
          return new Multisets.AbstractEntry<K>() {
            @Override

    }
    return changed;
  }

  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

    }

    @Override
    public ActionFuture<MultiGetResponse> multiGet(final MultiGetRequest request) {
        return client.multiGet(request);
    }

    @Override
    public void multiGet(final MultiGetRequest request, final ActionListener<MultiGetResponse> listener) {
        client.multiGet(request, listener);
    }

    @Override