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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _parse(reactor, directory, pemdir, *args, **kwargs):
 """ Parse a txacme endpoint description. :param reactor: The Twisted reactor. :param directory: ``twisted.python.url.URL`` for the ACME directory to use for issuing certs. :param str pemdir: The path to the certificate directory to use. """

    def colon_join(items):
        return ':'.join([item.replace(':', '\\:') for item in items])
    sub = colon_join(list(args) + ['='.join(item) for item in kwargs.items()])
    pem_path = FilePath(pemdir).asTextMode()
    acme_key = load_or_create_client_key(pem_path)
    return AutoTLSEndpoint(
        reactor=reactor,
        directory=directory,
        client_creator=partial(Client.from_url, key=acme_key, alg=RS256),
        cert_store=DirectoryStore(pem_path),
        cert_mapping=HostDirectoryMap(pem_path),
        sub_endpoint=serverFromString(reactor, sub))