private static @NotNull
  ValueContainer.IntIterator getIntIteratorOutOfFileSetObject(@Nullable Object input) {
    if (input == null) return EMPTY_ITERATOR;
    if (input instanceof Integer) {
      return new SingleValueIterator(((Integer)input).intValue());
    }
    return ((ChangeBufferingList)input).intIterator();
  }
private static @NotNull
  ValueContainer.IntIterator getIntIteratorOutOfFileSetObject(@Nullable Object input)