'Return a dict with all known URLs for this course image.
Current resolutions are:
raw = original upload from the user
small = thumbnail with dimensions CourseOverviewImageConfig.current().small
large = thumbnail with dimensions CourseOverviewImageConfig.current().large
If no thumbnails exist, the raw (originally uploaded) image will be
returned for all resolutions.'

@property
def image_urls(self):

    raw_image_url = self.course_image_url
    urls = {'raw': raw_image_url, 'small': raw_image_url, 'large': raw_image_url}
    if (hasattr(self, 'image_set') and CourseOverviewImageConfig.current().enabled):
        urls['small'] = (self.image_set.small_url or raw_image_url)
        urls['large'] = (self.image_set.large_url or raw_image_url)
    return self.apply_cdn_to_urls(urls)
