    def expires_in(self):
        """Property returning expiration in seconds from now

        or None
        """
        if self.expires_at:
            delta = self.expires_at - self.now()
            if isinstance(delta, timedelta):
                delta = delta.total_seconds()
            return delta
        else:
            return None
Property returning expiration in seconds from now

or None
jupyterhub/orm.py