How to use the lastversion.HolderFactory.HolderFactory.HOLDERS function in lastversion

def get_instance_for_repo(repo):
        holder_class = HolderFactory.HOLDERS['github']
        hostname = None
        known_repo = None
        for k, sc in HolderFactory.HOLDERS.items():
            known_repo = sc.is_official_for_repo(repo)
            if known_repo:
                holder_class = sc
                log.info('Using {} adapter'.format(k))
                break
            # TODO now easy multiple default hostnames per holder
            hostname = sc.get_matching_hostname(repo)
            if hostname:
                holder_class = sc
                break
        if known_repo:
            repo = known_repo['repo']
            # known repo tells us hosted domain of e.g. mercurical web