docs: 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))
              )