I'm using codeigniter 4 but when I try to call my own library I get the error `Undefined variable: utils`.

here's my code:

**/app/libraries/Utils.php**

```
<?php

namespace App\Libraries;

class Utils
{
    function generateRandomString($length = 10) {
        return substr(str_shuffle(str_repeat($x='0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ', ceil($length/strlen($x)) )),1,$length);
    }
}

```

**/app/Controllers/Users.php**

```
<?php

namespace App\Controllers;

use CodeIgniter\RESTful\ResourceController;
use CodeIgniter\API\ResponseTrait;
use App\Models\UserModel;
use App\Libraries\Utils;

class Users extends ResourceController
{
    ...
    public function do_reset_password()
    {
        $utils = new Utils();
        $str = $utils->generateRandomString(); // the error points to this line
    ...

```