'Given a dict of resolutions -> urls, return a copy with CDN applied.
If CDN does not exist or is disabled, just returns the original. The
URLs that we store in CourseOverviewImageSet are all already top level
paths, so we don\'t need to go through the /static remapping magic that
happens with other course assets. We just need to add the CDN server if
appropriate.'

def apply_cdn_to_urls(self, image_urls):

    cdn_config = AssetBaseUrlConfig.current()
    if (not cdn_config.enabled):
        return image_urls
    base_url = cdn_config.base_url
    return {resolution: self._apply_cdn_to_url(url, base_url) for (resolution, url) in image_urls.items()}
