add class to login page wordpress

1function add_blog_id_to_login_page( $classes ) {
2    $blog_id   = get_current_blog_id();
3    $classes[] = "blog-{$blog_id}";
4    return $classes;
5}
6
7add_filter( 'login_body_class', 'add_blog_id_to_login_page' );
8