def session(self):
        """
        http session interface, transparent proxy to requests.session
        """
        if self._session is None:
            self._session = requests.session()
            self._session.headers.update(
                {
                    "Authorization": "Bearer {}".format(self.token),
                    "User-Agent": "ads-api-client/{}".format(__version__),
                    "Content-Type": "application/json",
                }
            )
        return self._session
http session interface, transparent proxy to requests.session