/**
  * 
  * @param Bootstrap_Helper_Element $element
  * @param integer $priority
  */
 public function add($element, $is_active = FALSE, array $attributes = array(), $priority = 0)
 {
     $element_li = Bootstrap_Dropdown_Element::factory(array('element' => $element))->attributes($attributes);
     if ($is_active !== FALSE) {
         $element_li->attributes('class', 'active');
     }
     if ($element instanceof Bootstrap_Element_Button) {
         $element->attributes()->delete('class', '^btn');
     }
     if ($element instanceof Bootstrap_Dropdown) {
         $element_li->attributes('class', 'dropdown-submenu');
     }
     $this->_add($element_li, $priority);
     return $this;
 }
 protected function _build_content()
 {
     parent::_build_content();
     $this->_content = '<span' . (string) $this->attributes() . '>' . $this->get('text') . '</span>';
 }