docs: private ArrayDBIDs updateKNNsAfterDeletion(DBIDs ids) {
      SetDBIDs idsSet = DBIDUtil.ensureSet(ids);
      ArrayModifiableDBIDs rkNN_ids = DBIDUtil.newArray();
      for(DBIDIter iditer = relation.iterDBIDs(); iditer.valid(); iditer.advance()) {
        KNNList kNNs = storage.get(iditer);
        for(DBIDIter it = kNNs.iter(); it.valid(); it.advance()) {
          if(idsSet.contains(it)) {
            rkNN_ids.add(iditer);
            break;
          }
        }
      }
  
      // update the kNNs of the RkNNs
      List<? extends KNNList> kNNList = knnQuery.getKNNForBulkDBIDs(rkNN_ids, k);
      DBIDIter iter = rkNN_ids.iter();
      for(int i = 0; i < rkNN_ids.size(); i++, iter.advance()) {
        storage.put(iter, kNNList.get(i));
      }
  
      return rkNN_ids;
    }