def METHOD_NAME(cls, url, webpage):
    if not re.search(r'<script[^>]+src=["\']https://substackcdn.com/[^"\']+\.js', webpage):
        return
    mobj = re.search(r'{[^}]*["\']subdomain["\']\s*:\s*["\'](?P<subdomain>[^"]+)', webpage)
    if mobj:
        parsed = urllib.parse.urlparse(url)
        yield parsed._replace(netloc=f'{mobj.group("subdomain")}.substack.com').geturl()
        raise cls.StopExtraction()