protected function transformFieldset(Fieldset $fieldset)
    {
        $controls = [];

        foreach ($fieldset->controls() as $control) {
            $type = $control->get('type');

            if (!in_array($type, self::$protectedTypes)) {
                $controls[] = $this->transformControlField($control);
            }
        }

        $this->fieldsets[] = [
            'name'     => $fieldset->getName(),
            'controls' => $controls,
        ];
    }