export symbol and parameters file for MXNet models trained using Sagemaker

I have successfully trained a demo mxnet model based on symantec_segmentation notebook, however the exported model on S3 does not contain symbol JSON file (model_name-symbol.json) and parameters file (model_name-0000.params) and it doesn't look like there's a way to extract it from serialized inference model that is provided in model.tar.gz file.