def get_expiry_age(self, **kwargs):
        """Get the number of seconds until the session expires.

        Optionally, this function accepts `modification` and `expiry` keyword
        arguments specifying the modification and expiry of the session.
        """
        try:
            modification = kwargs['modification']
        except KeyError:
            modification = timezone.now()
        # Make the difference between "expiry=None passed in kwargs" and
        # "expiry not passed in kwargs", in order to guarantee not to trigger
        # self.load() when expiry is provided.
        try:
            expiry = kwargs['expiry']
        except KeyError:
            expiry = self.get('_session_expiry')

        if not expiry:   # Checks both None and 0 cases
            return settings.SESSION_COOKIE_AGE
        if not isinstance(expiry, datetime):
            return expiry
        delta = modification - expiry
        return delta.days * 86400 + delta.seconds
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.5/django/contrib/sessions/backends/base.py/SessionBase.get_expiry_age/swapped operands of `-`