code: public final void sendNotification(String uniqueIdentifier, SPFActionSendNotification action) {
          if (uniqueIdentifier == null || action == null) {
              throw new NullPointerException();
          }
  
          String actionJSON = action.toJSON();
          sendNotification(uniqueIdentifier, actionJSON);
      }
docs: Sends a notification to the remote SPF instance.
  
  @param uniqueIdentifier - the identifier of the sender.
  @param action           - the notification action.