When extending another packages' serializers you can `addAll` their serializers however I don't think there is a way to add all their BuilderFactories? It would be great if you can do this: ```dart import 'package:foobar/foobar.dart' as mypackage; // ... final Serializers serializers = (_$serializers.toBuilder() ..addAll(mypackage.serializers.serializers) ..addAllBuilderFactories(mypackage.serializers.builderFactories); ).build(); ``` It would also be nice to addAllPlugins too but this would be less useful.