@Override
  public int @NotNull [] keys() {
    Object[] entries = new EntrySetView<>(this).toArray();
    int[] result = new int[entries.length];
    for (int i = 0; i < entries.length; i++) {
      Entry<V> entry = (Entry<V>)entries[i];
      result[i] = entry.getKey();
    }
    return result;
  }
@Override
  public int @NotNull [] keys()