modification of DDPM and DDIM. We added arguments clip_sample_min and clip_sample_max, so that the user can choose to clip, but specify by which values (originally, it was done with -1 and 1, but this has proven ineffective with certain image ranges and with latent models).
VQ-VAE was missing an import
Patch-GAN and VQVAE have been reformatted after running autofix.
In response to discussion #492 and issue #494: