public static function widgetClass($alias)
    {
        $result = false;
        $module = static::instance();
        if (!empty($module) && !empty($module->_widgets[$alias])) {
            $config = $module->_widgets[$alias];
            if (is_string($config)) {
                $result = $config;
            } elseif (!empty($config['class'])) {
                $result = $config['class'];
            } else {
                throw new Exception("Shared widget '{$alias}' has wrong in configuration in module " . static::className());
            }
        }
        return $result;
    }