ONNX is a open format to represent deep learning models.
So I want to import neural networks from other frameworks via ONNX.
And the Mathematica 11.3 supports python now.
I think I can use ONNX-MXNet to export the mxnet.json and mxnet.params then just Import these.
But I have no idea about how to install packages on Python-ExternalSessions.
Here is an onnx-format file of Super Resolution Model.
How can I import this using Mathematica and Python-ExternalSessions?
This is incomplete answer because Mathematica doesn't support the latest version of mxnet.
Step 1
Install onnx-mxnet. Open Command Prompt and enter:
pip install onnx-mxnet 
Step 2
Download model and image. Run this code in Mathematica:
import mxnet as mx import onnx_mxnet import numpy as np sym, params = onnx_mxnet.import_model('C:/Users/Alexey/Documents/super_resolution.onnx') from PIL import Image img = Image.open('C:/Users/Alexey/Documents/super_res_input.jpg').resize((224, 224)) img_ycbcr = img.convert("YCbCr") img_y, img_cb, img_cr = img_ycbcr.split() test_image = np.array(img_y)[np.newaxis, np.newaxis, :, :] mod = mx.mod.Module(symbol=sym, data_names=['input_0'], context=mx.cpu(), label_names=None) mod.bind(for_training=False, data_shapes=[('input_0',test_image.shape)], label_shapes=None) mod.set_params(arg_params=params, aux_params=params, allow_missing=True, allow_extra=True) mod.save_checkpoint("super_resolution",1) net = Import["super_resolution-symbol.json", "MXNet"] 