public function register()
    {
        // Register Sub Providers
        $this->registerSubProviders(collect($this->subProviders));
        // Register bindings.
        $this->registerBindings(collect($this->bindings));
        // Register migrations.
        $this->registerMigrations(collect($this->migrations));
        // Register seeders.
        $this->registerSeeders(collect($this->seeders));
        // Register model factories.
        $this->registerFactories(collect($this->factories));
    }