def nack(self, channel_id=None, **kwargs):  # pragma: no cover
        """Send a negative read-acknowledgement to the service.

        Causes the channel's read point to move to its previous position
        prior to the last poll.

        Args:
            channel_id (str): The channel ID.
            **kwargs: Supported :meth:`~pancloud.httpclient.HTTPClient.request` parameters.

        Returns:
            requests.Response: Requests Response() object.

        Examples:
            Refer to ``event_nack.py`` example.

        """
        path = "/event-service/v1/channels/{}/nack".format(channel_id)
        r = self._httpclient.request(
            method="POST",
            url=self.url,
            path=path,
            **kwargs
        )
        return r