public function add_meta_boxes( $post_type )
    {    
        if ( in_array( $post_type, $this->settings['post_types'] )) {
            add_meta_box(
                $this->settings['id'],
                $this->settings['title'],
                array( $this, 'render' ),
                $post_type,
                $this->settings['context'],
                $this->settings['priority']
            );
        }
    }