/**
  * Return an instance of this class.
  */
 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;
 }
 /**
  * Get the instance for all the included classes
  */
 public function init()
 {
     Stripe_Checkout_Scripts::get_instance();
     Stripe_Checkout_Shortcodes::get_instance();
     if (is_admin()) {
         Stripe_Checkout_Admin::get_instance();
         Stripe_Checkout_Upgrade_Link::get_instance();
         Stripe_Checkout_Notices::get_instance();
         Stripe_Checkout_System_Status::get_instance();
     } else {
         Stripe_Checkout_Misc::get_instance();
         Stripe_Checkout_Functions::get_instance();
     }
 }