def invite(self, channel_name, user):
        """ https://api.slack.com/methods/channels.invite
        """
        channel_id = self.get_channel_id(channel_name)
        self.params.update({
            'channel': channel_id,
            'user':    user,
            })
        return FromUrl('https://slack.com/api/channels.invite', self._requests)(data=self.params).post()