AttributeError: 'model' object has no attribute 'module'

I have been follow pix2pixHD pytorch code for a while now.

I’m not quite sure why they use:

model.module.optimizer_G.zero_grad() instead of model.optimizer_G.zero_grad() link here

model.module.optimizer_D.zero_grad() instead of model.optimizer_D.zero_grad() link here

I couldn’t find module anywhere in there repo. Is it a pytorch thing?