Get all subsites of an user in WordPress

Get all subsites of an user in WordPress.hp

<?php

function show_my_sites_cb(  ) {
     if( ! is_user_logged_in() ){
        return '';
     }
     else{
        $blogs = '<ul>';
        $user_ID = get_current_user_id();
        $user_blogs = get_blogs_of_user( $user_id );
        foreach ($user_blogs as $user_blog) {
          $blogs .= '<li>'. $user_blog->blogname .'</li>';
        }
        $blogs .= '</ul>';
        return $blogs;
     }
}
add_shortcode('show_my_sites', 'show_my_sites_cb');