public void Update()
    {
        if (download_successful_events.Count > 0)
        {
            DownloadSuccessfulEvent successfulEvent = download_successful_events.Dequeue();
            successfulEvent.Callback();
        }

        if (downLoad_error_events.Count > 0)
        {
            DownLoadErrorEvent errorEvent = downLoad_error_events.Dequeue();
            errorEvent.Callback();
        }

        OnUpdate();
    }