docs: @Override
    public final boolean delete(DBIDRef id) {
      // find the leaf node containing o
      O obj = relation.get(id);
      IndexTreePath<DeLiCluEntry> deletionPath = findPathToObject(getRootPath(), obj, id);
      if(deletionPath == null) {
        return false;
      }
      deletePath(deletionPath);
      return true;
    }