'Takes a source url and a list of category objects and returns
a list of feed urls'

def get_feed_urls(self, source_url, categories):

    total_feed_urls = []
    for category in categories:
        kwargs = {'attr': 'type', 'value': 'application\\/rss\\+xml'}
        feed_elements = self.parser.getElementsByTag(category.doc, **kwargs)
        feed_urls = [e.get('href') for e in feed_elements if e.get('href')]
        total_feed_urls.extend(feed_urls)
    total_feed_urls = total_feed_urls[:50]
    total_feed_urls = [urls.prepare_url(f, source_url) for f in total_feed_urls]
    total_feed_urls = list(set(total_feed_urls))
    return total_feed_urls
