public virtual Task <AddPersistedFaceResult> AddFaceToFaceListAsync(string faceListId, string imageUrl,
                                                                     string userData = null, Rectangle targetFace = null)
 {
     return(PolicyService.ExecuteRetryAndCapture400Errors(
                "FaceService.AddFaceToFaceListAsync",
                ApiKeys.FaceRetryInSeconds,
                () =>
     {
         var result = FaceRepository.AddFaceToFaceListAsync(faceListId, imageUrl, userData, targetFace);
         return result;
     },
                null));
 }