In below example, I have written Python script to create the session and to add the link with the given channel. To do this, directly use below python code in your .py file

 Session = self.pool["im_chat.session"]
        newid = Session.create(cr, uid, {'user_ids': [(4, user_id)], 'channel_id': channel_id, 'anonymous_name' : anonymous_name}, context=context)
        return Session.session_info(cr, uid, [newid], context=context)
 def test_channel(self, cr, uid, channel, context=None):
        if not channel:
            return {}
        return {
            'url': self.browse(cr, uid, channel[0], context=context or {}).web_page,
            'type': 'ir.actions.act_url'
        } def get_info_for_chat_src(self, cr, uid, channel, context=None):
        url = self.pool.get('ir.config_parameter').get_param(cr, uid, 'web.base.url')
        chan = self.browse(cr, uid, channel, context=context)
        return {
            "url": url,
            'buttonText': chan.button_text,
            'inputPlaceholder': chan.input_placeholder,
            'defaultMessage': chan.default_message,
            "channelName": chan.name,
        }