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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 rfc19242long(s):
 """Convert an RFC 1924 IPv6 address to a network byte order 128-bit integer. True True True True True :param ip: RFC 1924 IPv6 address :type ip: str :returns: Network byte order 128-bit integer or ``None`` if ip is invalid. """

    global _RFC1924_REV
    if not _RFC1924_RE.match(s):
        return None
    if _RFC1924_REV is None:
        _RFC1924_REV = {v: k for k, v in enumerate(_RFC1924_ALPHABET)}
    x = 0
    for c in s:
        x = x * 85 + _RFC1924_REV[c]
    if x > MAX_IP:
        return None
    return x