implements Serializable {
    final Map<E, Integer> backingMap = Maps.newHashMap();

    @Override
    public int size() {
      return Multisets.linearTimeSizeImpl(this);
    }

    @Override
    public void clear() {
      throw new UnsupportedOperationException();
    }

    @Override
    public int count(@Nullable Object element) {

      implements Serializable {
    final Map<E, Integer> backingMap = Maps.newHashMap();

    @Override
    public int size() {
      return Multisets.linearTimeSizeImpl(this);
    }

    @Override
    public void clear() {
      throw new UnsupportedOperationException();
    }

    @Override
    public int count(@Nullable Object element) {