I can convert the segmentation model with no error message, but the preview is not showing any predictions

## ❓Question
Hello,
This is the model I am trying to convert: https://github.com/cnpcshangbo/crack_detection/tree/coreML#pre-trained-model
My code for conversion is: https://github.com/cnpcshangbo/crack_detection/blob/coreML/Code/conver2CoreML.py
Currently, it works without errors, but the converted mode doesn't output anything. Here's a video to show how I converted:
https://capture.dropbox.com/Wx1Wl5A9KVGnYDfj
Hope to get some suggestions on how to debug this conversion?
Thanks,
Bo

Start by reviewing the linked pretrained model and Code/conver2CoreML.py, then reproduce the conversion and preview behavior described in the issue. Done means identifying why the converted model produces no preview predictions and documenting or validating a working conversion; the issue provides no project test or additional debugging details.

Written by the indexing model from the issue text.