private function addSubForms(FormBuilderInterface $builder, array $choiceViews, array $options)
    {
        foreach ($choiceViews as $name => $choiceView) {
            // Flatten groups
            if (\is_array($choiceView)) {
                $this->addSubForms($builder, $choiceView, $options);
                continue;
            }

            if ($choiceView instanceof ChoiceGroupView) {
                $this->addSubForms($builder, $choiceView->choices, $options);
                continue;
            }

            $this->addSubForm($builder, $name, $choiceView, $options);
        }
    }