/**
  * Get an instance of the page extension but don't initialize it.
  *
  * Useful for using some methods during AJAX call.
  *
  * @return WPCF_GUI_Term_Field_Editing
  * @since 2.1
  */
 public static function get_instance()
 {
     if (null == self::$instance) {
         self::$instance = new self();
     }
     return self::$instance;
 }
 public static function initialize()
 {
     if (null == self::$instance) {
         self::$instance = new self();
     }
 }