/**
  * @param $slug
  * @param $tab
  * @param $setting
  */
 public static function init($slug, $tab, $setting)
 {
     $tab['slug'] = $slug;
     self::$setting = $setting;
     self::$setting_tab = $tab;
     add_action('load_' . $setting::HW_SETTINGS_PAGE . '_' . $setting::valid_tab_slug($slug), __CLASS__ . '::replyToAddFormElements');
 }