code: def _images_succeeded(cls, session):
          
          for image, store in cls._deleted_images:
              for stored_image, _ in cls._stored_images:
                  if stored_image.object_type == image.object_type and \
                     stored_image.object_id == image.object_id and \
                     stored_image.width == image.width and \
                     stored_image.height == image.height and \
                     stored_image.mimetype == image.mimetype:
                      break
              else:
                  store.delete(image)
          cls._stored_images.clear()
          cls._deleted_images.clear()
docs: Clears the :attr:`_stored_images` set and deletes actual
          files that are marked as deleted in the storage
          if the ongoing transaction has committed.