def get_refresh_token(self):
        """Method to return the current requests' refresh_token.

        :returns: Access token or None
        :rtype: str

        .. versionadded:: 1.2
        """
        try:
            credentials = OAuth2Credentials.from_json(
                self.credentials_store[g.oidc_id_token['sub']])
            return credentials.refresh_token
        except KeyError:
            logger.debug("Expired ID token, credentials missing",
                         exc_info=True)
            return None