public function configure()
 {
     $this->setWidgets(array('sf_plop_cms_enabled_slot_templates' => new sfWidgetFormChoice(array('multiple' => true, 'expanded' => true, 'choices' => self::getSlots(), 'default' => sfPlop::getEnabledSlots(), 'label' => 'Enabled slot templates'))));
     $this->setValidators(array('sf_plop_cms_enabled_slot_templates' => new sfValidatorChoice(array('multiple' => true, 'choices' => array_keys(self::getSlots())))));
     parent::configure();
 }