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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 has_expired(self, lifetime, now=None):
 """Report if the session key has expired. :param lifetime: A :class:`datetime.timedelta` that specifies the maximum age this :class:`SessionID` should be checked against. :param now: If specified, use this :class:`~datetime.datetime` instance instead of :meth:`~datetime.datetime.utcnow()` as the current time. """

        now = now or datetime.utcnow()
        return now > self.created + lifetime