@Override
  public @NotNull RandomAccessIntContainer ensureContainerCapacity(int count) {
    int newSize = mySetLength + count;
    if (newSize < mySet.length) return this;
    if (newSize > ChangeBufferingList.MAX_FILES) {
      return new IdBitSet(this, count);
    }

    newSize = ChangeBufferingList.calcNextArraySize(mySet.length, newSize);
    assert newSize < Short.MAX_VALUE;

    int[] newSet = new int[newSize]; // todo slightly increase size and compact
    System.arraycopy(mySet, 0, newSet, 0, mySetLength);
    mySet = newSet;

    return this;
  }
@Override
  public @NotNull RandomAccessIntContainer ensureContainerCapacity(int count)