/**
  * Removes user from waitlist on purchase if persistent waitlists are enabled
  *
  * @static
  * @param  object $order WC_Order object
  * @access public
  * @return void
  */
 public static function check_order_for_waitlisted_items($order)
 {
     if (self::persistent_waitlists_are_disabled()) {
         return;
     }
     if (self::automatic_mailouts_are_disabled()) {
         return;
     }
     $user = get_user_by('id', $order->user_id);
     foreach ($order->get_items() as $item) {
         if ($item['id'] > 0) {
             $_product = $order->get_product_from_item($item);
             $waitlist = new Pie_WCWL_Waitlist($_product);
             $waitlist->unregister_user($user);
         }
     }
 }