'A cached version of self.images.all().
Because django-cache-machine doesn\'t cache empty lists.'

def get_images(self):

    cache_key = (self.images_cache_key % self.id)
    images = cache.get(cache_key)
    if (images is None):
        images = list(self.images.all())
        cache.add(cache_key, images, CACHE_TIMEOUT)
    return images
