docs: def argset(name, *args, **kwargs):
      """
      Decorator to add sets of required mutually exclusive args to subcommands.
      """
      def _arg(f):
          if not hasattr(f, '_subcommand_argsets'):
              f._subcommand_argsets = {}
          f._subcommand_argsets.setdefault(name, []).append((args, kwargs))
          return f
      return _arg