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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_expires(expires):
 """ Parse the 'expires' attribute, guessing what format it is in and returning a datetime """

    # none is used to signify positive infinity
    if expires is None or expires in ('never', 'infinity'):
        return 'infinity'

    try:
        return dateutil.parser.parse(unicode(expires))
    except ValueError as exc:
        pass

    try:
        # use parsedatetime for "human readable" time specs
        exp = pdt.parse(expires)[0]
        # and convert to datetime
        return datetime.datetime.fromtimestamp(time.mktime(exp))
    except ValueError as exc:
        pass

    raise NipapValueError("Invalid date specification for expires")