TypeError: unsupported operand type(s) for +: 'NoneType' and 'int'

[Nikki-Gu]

In the file "detect_FP_vessels_w_DNN.py", line 69, the code model = smp.Unet('vgg13',None).to(device) has input the 'NoneType' into the smp.Unet function, causing the following error: TypeError: unsupported operand type(s) for +: 'NoneType' and 'int'

So what does the input parameter 'None' means in the above code? Should I change it to other parameters to make this code working? Looking forward to your reply!