How to set up Authorisation Factory from database?

I am reading the docs at https://doc.nette.org/…thentication to create roles from a database.

I am getting error when connecting to database.

Error
Using $this when not in object context

Of course, create() is a static function, and $this cannot be used, but are roles loaded from database here?
If $this is replaced with self:: then the error will be that create() is not callable.
How do I load the roles from the database correctly?

This is the code..

<?php
declare(strict_types=1);

namespace App\Model;

class AuthorizationFactory
{
        private $context;

        public function __construct( Nette\Database\Context $context )
        {
                $this->context = $context;
        }


        public static function create(): \Nette\Security\Permission
        {
                $acl = new \Nette\Security\Permission;

                // if we want, we can load roles from database
                $roles = $this->context->table('user_group_role');

                $acl->addRole('admin');
                $acl->addRole('guest');

                $acl->addResource('backend');

                $acl->allow('admin', 'backend');
                $acl->deny('guest', 'backend');

                // example A: role admin has lower weight than role guest
                $acl->addRole('john', ['admin', 'guest']);
                $acl->isAllowed('john', 'backend'); // false

                // example B: role admin has greater weight than role guest
                $acl->addRole('mary', ['guest', 'admin']);
                $acl->isAllowed('mary', 'backend'); // true

                return $acl;
        }
}
?>