How to use the cmd2.with_argparser_and_unknown_args function in cmd2

    @cmd2.with_argparser_and_unknown_args(mumble_parser)
    def do_mumble(self, opts, arg):
        """Mumbles what you tell me to."""
        repetitions = opts.repeat or 1
        #arg = arg.split()
        for _ in range(min(repetitions, self.maxrepeats)):
            output = []
            if random.random() < .33:
                output.append(random.choice(self.MUMBLE_FIRST))
            for word in arg:
                if random.random() < .40:
                    output.append(random.choice(self.MUMBLES))
                output.append(word)
            if random.random() < .25:
                output.append(random.choice(self.MUMBLE_LAST))
            self.poutput(' '.join(output))

    @cmd2.with_argparser_and_unknown_args(argparse.ArgumentParser(), ns_provider=namespace_provider)
    def do_test_argparse_with_list_ns(self, args, extra):
        self.stdout.write('{}'.format(args.custom_stuff))

    @cmd2.with_argparser_and_unknown_args(base_parser)
    def do_base(self, args):
        """Base command help"""
        func = getattr(args, 'func', None)
        if func is not None:
            # Call whatever subcommand function was selected
            func(self, args)
        else:
            # No subcommand was provided, so call help
            self.do_help('base')

    @cmd2.with_argparser_and_unknown_args(greet_parser)
    def do_greet(self, opts, arg):
        arg = ''.join(arg)
        if opts.shout:
            arg = arg.upper()
        self.stdout.write(arg + '\n')

    @cmd2.with_argparser_and_unknown_args(known_parser)
    def do_speak(self, args, extra):
        """Repeat what you tell me to."""
        words = []
        for word in extra:
            if word is None:
                word = ''
            if args.piglatin:
                word = '%s%say' % (word[1:], word[0])
            if args.shout:
                word = word.upper()
            words.append(word)
        repetitions = args.repeat or 1
        for i in range(min(repetitions, self.maxrepeats)):
            self.stdout.write(' '.join(words))
            self.stdout.write('\n')

    @cmd2.with_argparser_and_unknown_args(pprint_parser)
    def do_pprint(self, args, unknown):
        """Print the options and argument list this options command was called with."""
        self.poutput('oprint was called with the following\n\toptions: {!r}\n\targuments: {}'.format(args, unknown))

    @cmd2.with_argparser_and_unknown_args(dir_parser)
    def do_dir(self, args, unknown):
        """List contents of current directory."""
        # No arguments for this command
        if unknown:
            self.perror("dir does not take any positional arguments:")
            self.do_help('dir')
            self.last_result = cmd2.CommandResult('', 'Bad arguments')
            return

        # Get the contents as a list
        contents = os.listdir(self.cwd)

        fmt = '{} '
        if args.long:
            fmt = '{}\n'
        for f in contents: