Returns the expiration datetime
        :return datetime: The datetime this token expires

def expiration_datetime(self):
        """
        Returns the expiration datetime
        :return datetime: The datetime this token expires
        """
        expires_at = self.get('expires_at')
        if expires_at is None:
            # consider it is expired
            return dt.datetime.now() - dt.timedelta(seconds=10)
        expires_on = dt.datetime.fromtimestamp(expires_at) - dt.timedelta(seconds=EXPIRES_ON_THRESHOLD)
        if self.is_long_lived:
            expires_on = expires_on + dt.timedelta(days=90)
        return expires_on