'Walks available urls and returns them by type. Only
appropriate in opensearch v1.1 where there can be multiple
query targets. Returns none if no such type is found.
url = description.get_url_by_type(\'application/rss+xml\')'

def get_url_by_type(self, type):

    for url in self.urls:
        if (url.type == type):
            return url
    return None
