Where can I find the masks in the data ?

[SherlockLeon]

Based on your code, I presume that there should be mask in the dataset Casia2, but the dataset I downloaded from the dataset download link you gave doesn't have a mask, it only has Au and Tp in it

mask = io.imread(self.input_path + '/masks/' + im_name + '_gt.png')

[kPsarakis]

I think we got it from here https://github.com/namtpham/casia2groundtruth