docs: protected ArrayDBIDs rowsBitsetToIDs(BitSet rows) {
      ArrayModifiableDBIDs rowIDs = DBIDUtil.newArray(rows.cardinality());
      DBIDArrayIter iter = this.rowIDs.iter();
      for(int i = rows.nextSetBit(0); i >= 0; i = rows.nextSetBit(i + 1)) {
        iter.seek(i);
        rowIDs.add(iter);
      }
      return rowIDs;
    }