def METHOD_NAME(repo):
    url = repo + 'repodata/repomd.xml'
    repomd = requests.get(url)
    if not repomd.ok:
        return None
    root = ET.fromstring(bytes(repomd.text, encoding='utf-8'))
    cs = root.find(
        './/{http://linux.duke.edu/metadata/repo}data[@type="updateinfo"]/{http://linux.duke.edu/metadata/repo}location')
    try:
        url = repo + cs.attrib['href']
    except AttributeError:
        return None
    repomd = requests.get(url).content
    root = ET.fromstring(decompress(repomd))
    return root.find('.//id').text