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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 _cookie_expiration(self):
 """Return the expiration timestamp for the session cookie. :rtype: datetime """

        value = (datetime.datetime.utcnow() +
                 datetime.timedelta(seconds=self._session_duration))
        LOGGER.debug('Cookie expires: %s', value.isoformat())
        return value