docs: @Override
    public ArrayModifiableDBIDs order(DBIDs ids) {
      ArrayModifiableDBIDs res = DBIDUtil.newArray(ids.size());
      for(DBIDIter it = this.ids.iter(); it.valid(); it.advance()) {
        if(ids.contains(it)) {
          res.add(it);
        }
      }
      return res;
    }