pssr# Point-Scanning Super-Resolution 2 API Reference train train_paired approximate_crappifier train_crappifier predict predict_images predict_collage test_metrics data ImageDataset SlidingDataset PairedImageDataset PairedSlidingDataset preprocess_dataset crappifiers Crappifier MultiCrappifier Poisson AdditiveGaussian SaltPepper models ResUNet RDResUNet SwinIR util SSIMLoss reassemble_sheets normalize_preds pixel_metric CLI