private Optional<Model> modelOf(Version version) {
        if (activeApplicationVersions.isEmpty()) return Optional.empty();
        return activeApplicationVersions.get().get(version).map(Application::getModel);
    }
Builds activated versions of the right model versions

@author bratseth
configserver/src/main/java/com/yahoo/vespa/config/server/modelfactory/ActivatedModelsBuilder.java