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);
      return (values == null) ? 0 : values.size();
    }

    @Override
    public int remove(@Nullable Object element, int occurrences) {