${cmd_name}: get the structure of the specified message

        ${cmd_usage}
        ${cmd_option_list}

def do_struct(self, subcmd, opts, message):
        """${cmd_name}: get the structure of the specified message

        ${cmd_usage}
        ${cmd_option_list}
        """
        client = MdClient(self.maildir, filesystem=self.filesystem)
        as_json = getattr(opts, "json", False)
        client.getstruct(message, as_json=as_json, stream=self.stdout)