private function copyHelpers()
    {
        // copy Notifications
        $this->copyFilesFromSource($this->appPath . 'Helpers', app_path('Helpers'));

        // copy HelperServiceProvider
        $source = $this->appPath . "Providers{$this->ds}HelperServiceProvider.php";
        $this->copyFilesFromSource($source, app_path('Providers'));

        $this->line("Remember to add 'App\Providers\HelperServiceProvider::class,' in your 'config/app.php' in 'providers'");
    }