static function init()
 {
     $prefix = '_pan_';
     // A lista de sites
     $sites = wp_get_sites();
     if ($sites) {
         $sites_dropdown = array();
         foreach ($sites as $site) {
             if ($site['blog_id'] == 1) {
                 continue;
             }
             $sites_dropdown[] = array('label' => get_blog_details($site['blog_id'])->blogname, 'value' => $site['blog_id']);
         }
     }
     self::$custom_meta_fields = array(array('label' => __('Publication Source', 'panamazonica'), 'description' => '', 'id' => $prefix . 'fonte', 'type' => 'text', 'description' => ''), array('label' => __('Year', 'panamazonica'), 'description' => '', 'id' => $prefix . 'ano', 'type' => 'text', 'description' => ''), array('label' => __('Place', 'panamazonica'), 'description' => '', 'id' => $prefix . 'local', 'type' => 'text', 'description' => ''), array('label' => __('Author', 'panamazonica'), 'description' => '', 'id' => $prefix . 'autor', 'type' => 'text', 'description' => ''), array('label' => __('Collaborators', 'panamazonica'), 'description' => '', 'id' => $prefix . 'colaboradores', 'type' => 'text', 'description' => ''), array('label' => __('Language', 'panamazonica'), 'description' => '', 'id' => $prefix . 'idioma', 'type' => 'select', 'options' => array(array('label' => __('Portuguese', 'panamazonica'), 'value' => 'pt'), array('label' => __('Spanish', 'panamazonica'), 'value' => 'es'), array('label' => __('English', 'panamazonica'), 'value' => 'en'))), array('label' => __('Link', 'panamazonica'), 'description' => '', 'id' => $prefix . 'link', 'type' => 'upload', 'description' => 'Fill in the field with a link or upload a file.'));
     add_action('init', array(__CLASS__, 'register'));
     add_action('add_meta_boxes', array(__CLASS__, 'add_meta_box'));
     add_action('save_post', array(__CLASS__, 'save_postdata'));
     add_action('pre_get_posts', array(__CLASS__, 'pre_get_posts'));
     //add_filter('menu_order', array(__CLASS__, 'change_menu_label'));
     //add_filter('custom_menu_order', array(__CLASS__, 'custom_menu_order'));
 }