code: public function admin() {
  
  		$this->set_options();
  
  		$namespace    = Module::CustomRatingGrifus()->getOption( 'namespaces' );
  		$module_pages = Module::CustomRatingGrifus()->getOption( 'pages' );
  
  		App::main()->set_menus( $module_pages, $namespace['admin-page'] );
  
  		add_action( 'add_meta_boxes', [ $this->rating, 'add_meta_boxes' ], 10, 2 );
  		add_action( 'save_post', [ $this->rating, 'restart_rating' ], 1, 3 );
  		add_action( 'save_post', [ $this->rating, 'update_rating' ], 10, 3 );
  	}
docs: Admin initializer method.
  
  @uses add_action() → hooks a function on to a specific action