docs: public static <V extends NumberVector> NumberVector.Factory<V> getNumberVectorFactory(Relation<V> relation) {
      final VectorFieldTypeInformation<V> type = assumeVectorField(relation);
      @SuppressWarnings("unchecked")
      final NumberVector.Factory<V> factory = (NumberVector.Factory<V>) type.getFactory();
      return factory;
    }