sfWidgetFormChoice formatter - every <li> put in new line

sfWidgetFormChoiceFormatter.php

    /**
     * Metoda konfiguruje formularz
     */
     public function configure()
     {
        $this->widgetSchema['cities'] = new sfWidgetFormChoice(array(
                    'expanded' => true,
                    'multiple' => true,
                    'choices' => Doctrine_Core::getTable('hall')->getListNameForOpenHall(),
                    'renderer_options' => array('formatter' => array($this, 'formatter'))
                ));
     }

    /**
     * Metoda formatuje obiekt sfWidgetFormChoice - dzieli elementy <li> listy
     * tak by kazdy znalazl sie w nowej linii
     * 
     * @param sfWidget $widget
     * @param array $inputs
     * @return string
     */
    public function formatter($widget, $inputs)
    {
        $rows = array();
        $separator = '<br />';

        foreach ($inputs as $i => $input) {
            $rows[] = $widget->renderContentTag(
                    'li', $input['input'] . ' ' . $input['label'], ($i % 2 > 0 ? array('class' => 'pair') : array('class' => 'impair'))
            );
        }

        return $widget->renderContentTag('ul', implode($separator, $rows), array('class' => 'radio_list'));
    }