docs: private Database buildDerivatorDB(Relation<ParameterizationFunction> relation, DBIDs ids) {
      ProxyDatabase proxy = new ProxyDatabase(ids);
      int dim = dimensionality(relation);
      SimpleTypeInformation<DoubleVector> type = new VectorFieldTypeInformation<>(DoubleVector.FACTORY, dim);
      MaterializedRelation<DoubleVector> prep = new MaterializedRelation<>(type, ids);
      proxy.addRelation(prep);
  
      // Project
      for(DBIDIter iter = ids.iter(); iter.valid(); iter.advance()) {
        prep.insert(iter, DoubleVector.wrap(relation.get(iter).getColumnVector()));
      }
      return proxy;
    }