Gets list of image tensors from lists of Image objects, as a tuple of original, generated and real(target) images.

def _get_image_tensors(self)->([Tensor], [Tensor], [Tensor]):
        "Gets list of image tensors from lists of Image objects, as a tuple of original, generated and real(target) images."
        orig_images, gen_images, real_images = [], [], []
        for image_set in self.image_sets:
            orig_images.append(image_set.orig.px)
            gen_images.append(image_set.gen.px)
            real_images.append(image_set.real.px) 
        return orig_images, gen_images, real_images