${cmd_name}: list messages in the specified folder in JSON format

        ${cmd_usage}

def do_lisp(self, subcmd, opts, folder=""):
        """${cmd_name}: list messages in the specified folder in JSON format

        ${cmd_usage}
        """
        client = MdClient(self.maildir, filesystem=self.filesystem)
        client.lisp(
            foldername=folder,
            stream=self.stdout, 
            reverse=getattr(opts, "reverse", False),
            since=float(getattr(opts, "since", -1))
            )