/**
  * Returns the singleton instance of the class.
  *
  * @return object The CP_Plugin_Activation object.
  */
 public static function get_instance()
 {
     if (!isset(self::$instance) && !self::$instance instanceof CP_Plugin_Activation) {
         self::$instance = new CP_Plugin_Activation();
     }
     return self::$instance;
 }