public function sidebarClass($classes = [])
    {
        $classes = !is_array($classes) ? explode(' ', $classes) : $classes;
        $classes[] = sprintf('sidebar-%s', $this->template);
        $classes[] = 'sidebar';
        $classes[] = 'col-sm-4 col-md-3';

        $classes = apply_filters('novusopress_view_sidebar_classes', $classes);
        $output = sprintf('class="%s"', implode(' ', $classes));

        return apply_filters('novusopress_view_sidebar_class_output', $output);
    }