docs: public boolean checkSignature(PaymentNotification notification) {
          SortedMap<String, Object> notificationMap = JsonMapper.nonEmptyMapper().getMapper().convertValue(notification, SortedMap.class);
          notificationMap.putAll(notification.getOthers());
          notificationMap.remove("sign");
          return notification.getSign().equals(SignatureUtil.sign(notificationMap, paySetting.getKey()));
      }