docs: def apply2parser(cmd_proxy, parser):
      """
      Apply a CmdProxy's arguments and options
      to a parser of argparse.
      :type cmd_proxy: callable or CmdProxy
      :type parser: cmdtree.parser.AParser
      :rtype: cmdtree.parser.AParser
      """
      if isinstance(cmd_proxy, CmdProxy):
          parser_proxy = cmd_proxy.meta.parser
          _apply2parser(
              parser_proxy.arguments,
              parser_proxy.options,
              parser,
          )
      return parser