    vae = None

unet = UNet2DConditionModel.from_pretrained(
    args.pretrained_model_name_or_path, subfolder="unet", revision=args.revision
) Then, it’s time to create the training dataset and DataLoader from DreamBoothDataset:   Copied train_dataset = DreamBoothDataset(
    instance_data_root=args.instance_data_dir,
    instance_prompt=args.instance_prompt,
    class_data_root=args.class_data_dir if args.with_prior_preservation else None,
  