Runtime generation of uploaded file name (Django)

snippet.py

@deconstructible
class RandomFileName(object):
    def __init__(self, path):
        self.path = os.path.join(path, "%s%s")

    def __call__(self, _, filename):
        extension = os.path.splitext(filename)[1]
        return self.path % (uuid.uuid4(), extension)

image = models.ImageField(verbose_name=_('Image'), upload_to=RandomFileName('backgrounds'),
                          help_text=_('Maximum size: 5 MB'))