def post_message(self, channel, text, **kwargs):
        """ https://api.slack.com/methods/chat.postMessage
        """
        if not channel.startswith('#'):
            channel = '#' + channel
        self.params.update({
            'channel': channel,
            'text':    text,
            })
        if kwargs:
            self.params.update(kwargs)
        return FromUrl('https://slack.com/api/chat.postMessage', self._requests)(data=self.params).post()