public function buildView(FormView $view, FormInterface $form, array $options)
    {
        foreach ($view->vars['choices'] as $choice) {
            $dataNode = $choice->data;
            $level = $this->propertyAccessor->getValue($dataNode, 'lvl');

            $choice->label = str_repeat(str_repeat('&#160;', $level), 4).$choice->label;
        }
    }