First, we feed the noise to the generator and it will output the fake image, :

fake_x = generator(z)

Now we feed the real image to discriminator and get the probability of the real image being real:

D_logits_real = discriminator(x)

Similarly, we feed the fake image to discriminator and get the probability of the fake image being real:

D_logits_fake = discriminator(fake_x,reuse=True)