docs: public void setDBIDs(DBIDs ids) {
      this.idrep.setDBIDs(ids);
      // Update relations.
      for (Relation<?> orel : this.relations) {
        if (orel instanceof ProxyView) {
          ((ProxyView<?>) orel).setDBIDs(this.idrep.getDBIDs());
        }
      }
    }