@Override
    public boolean contains(@Nullable Object element) {
      return multimap.containsKey(element);
    }

    @Override
    public Iterator<K> iterator() {
      return Maps.keyIterator(multimap.entries().iterator());
    }

    @Override
    public int count(@Nullable Object element) {
      Collection<V> values = Maps.safeGet(multimap.asMap(), element);