orderby postviews faq

function alter_query_for_faq($query) {
    if ( !is_admin() && $query->is_main_query() && is_post_type_archive( 'faq' ) ) {
        $query->set('posts_per_page', '20');
        if ( class_exists( 'Post_Views_Counter' ) ) {
            $query->set('orderby', 'post_views');
            $query->set('order', 'DESC');
            $query->set('suppress_filters', false);
        } else {
            $query->set('orderby', 'rand');
        }
    }
}
add_action('pre_get_posts','alter_query_for_faq');