@classmethod
def normalize(cls, raw_status):
    """Turn a status into a canonical status value.

        If the status from the version discovery document does not match one
        of the known values, it will be set to 'UNKNOWN'.

        :param str raw_status: Status value from a discovery document.

        :returns: A canonicalized version of the status. Valid values
                  are CURRENT, SUPPORTED, DEPRECATED, EXPERIMENTAL and UNKNOWN
        :rtype: str
        """
    status = raw_status.upper()
    if status == 'STABLE':
        status = cls.CURRENT
    if status not in cls.KNOWN:
        status = cls.UNKNOWN
    return status
