public static int InstanceAssetsAsync(
     string[] addresses,
     OnAssetProgress progressCallback,
     OnAssetComplete completeCallback,
     OnAssetsProgress progressesCallback,
     OnAssetsComplete completesCallback,
     AsyncPriority priority = AsyncPriority.Default,
     SystemObject userdata  = null)
 {
     if (loader != null)
     {
         return(loader.InstanceAssetsAsync(addresses, progressCallback, completeCallback, progressesCallback, completesCallback, priority, userdata));
     }
     return(-1);
 }