public void onDone(CompletionCode code, String message) {
        synchronized (this) {
            completed = true;
            result = new Result();
            result.code = code;
            result.message = message;
            notifyAll();
        }
    }
Callback called when the visitor is done.

@param code the completion code
@param message an optional error message
documentapi/src/main/java/com/yahoo/documentapi/VisitorControlHandler.java