def update_token(self, response_json, **kwargs):
        """ Update access_token, refresh_token and token_expiry from the
        response body.
        The response must be converted to a json object before being passed as
        a parameter

        :param response_json: the response body to use.
        :param token_identifier: the user identifier for the token
        """
        self.token_identifier = kwargs.pop(
            'token_identifier',
            self.token_identifier
        )
        self.access_token = response_json['access_token']
        self.token_expiry = int(time.time()) + response_json['expires_in']

        if 'refresh_token' in response_json:
            self.refresh_token = response_json['refresh_token']