I am the beginner of Pytorch. And now I want to train a GAN. I have checked many different implement of GAN. I found that when update the discriminator will use the detach function to avoid update the generator. But why when update the generator not use the detach? Example: https://github.com/eriklindernoren/PyTorch-GAN/blob/master/implementations/context_encoder/context_encoder.py 10