public static function get_instance()
 {
     // If the single instance hasn't been set, set it now.
     if (null == self::$instance) {
         self::$instance = new self();
     }
     return self::$instance;
 }
 public function init()
 {
     Stripe_Subscriptions_Admin::get_instance();
     Stripe_Subscriptions_Scripts::get_instance();
     Stripe_Subscriptions_Functions::get_instance();
     Stripe_Subscriptions_Shortcodes::get_instance();
 }