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

    @Override
    public int count(@CheckForNull Object element) {
      Collection<V> values = Maps.safeGet(multimap.asMap(), element);
      return (values == null) ? 0 : values.size();
    }

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

  }

  /**
   * Delegates to {@link Map#get}. Returns {@code null} on {@code ClassCastException} and {@code
   * NullPointerException}.
   */
  @CheckForNull
  static <V extends @Nullable Object> V safeGet(Map<?, V> map, @CheckForNull Object key) {
    checkNotNull(map);
    try {
      return map.get(key);
    } catch (ClassCastException | NullPointerException e) {
      return null;
    }
  }