Creating my custom classes with Laravel Artisan [Laravel 8]

I'm trying to create a command that generates a class in the Services directory using the make:service command in Laravel 8. I followed the steps of this post.

class ServiceMakeCommand extends GeneratorCommand
{
    protected $name = 'make:service';
    protected $signature = 'make:service {name: Create your own service}';
    protected $description = 'Create a service for repository pattern';
    protected $type = 'Service';

    protected function getStub()
    {
        return app_path('Console/Stubs/service.stub');
    }

    protected function getDefaultNamespace($rootNamespace)
    {
        return $rootNamespace . '\Services';
    }
}

Also, I create my template stub.

<?php

namespace App\Service;

class DummyClass
{

}

But I get this error when I try to run this command.

php artisan make:service ProductService

Error

The "name" argument does not exist.

What does it mean?