code: private ClientNotificationArea getInboxIfAvailable(int clientID, JSONConverter converter) {
          final ClientNotificationArea inbox = inboxes.get(clientID);
  
          if (inbox == null) {
              throw ErrorHelper.createRESTHandlerJsonException(new RuntimeException("The requested clientID is no longer available because it timed out."),
                                                               converter,
                                                               APIConstants.STATUS_GONE);
          }
  
          return inbox;
      }
docs: This method returns the client inbox or throws an error if the client ID has timed out