How to use the docopt.Argument function in docopt

if token in '([':
        tokens.move()
        matching, pattern = {'(': [')', Required], '[': [']', Optional]}[token]
        result = pattern(*parse_expr(tokens, options))
        if tokens.move() != matching:
            raise tokens.error("unmatched '%s'" % token)
        return [result]
    elif token == 'options':
        tokens.move()
        return [OptionsShortcut()]
    elif token.startswith('--') and token != '--':
        return parse_long(tokens, options)
    elif token.startswith('-') and token not in ('-', '--'):
        return parse_shorts(tokens, options)
    elif token.startswith('<') and token.endswith('>') or token.isupper():
        return [Argument(tokens.move())]
    else:
        return [Command(tokens.move())]

def parse_argv(tokens, options, options_first=False):
    """Parse command-line argument vector.

    If options_first:
        argv ::= [ long | shorts ]* [ argument ]* [ '--' [ argument ]* ] ;
    else:
        argv ::= [ long | shorts | argument ]* [ '--' [ argument ]* ] ;

    """
    parsed = []
    while tokens.current() is not None:
        if tokens.current() == '--':
            return parsed + [Argument(None, v) for v in tokens]
        elif tokens.current().startswith('--'):
            parsed += parse_long(tokens, options)
        elif tokens.current().startswith('-') and tokens.current() != '-':
            parsed += parse_shorts(tokens, options)
        elif options_first:
            return parsed + [Argument(None, v) for v in tokens]
        else:
            parsed.append(Argument(None, tokens.move()))
    return parsed

if token in '([':
        tokens.move()
        matching, pattern = {'(': [')', Required], '[': [']', Optional]}[token]
        result = pattern(*parse_expr(tokens, options))
        if tokens.move() != matching:
            raise tokens.error("unmatched '%s'" % token)
        return [result]
    elif token == 'options':
        tokens.move()
        return [OptionsShortcut()]
    elif token.startswith('--') and token != '--':
        return parse_long(tokens, options)
    elif token.startswith('-') and token not in ('-', '--'):
        return parse_shorts(tokens, options)
    elif token.startswith('<') and token.endswith('>') or token.isupper():
        return [Argument(tokens.move())]
    else:
        return [Command(tokens.move())]

def single_match(self, left):
        for n, pattern in enumerate(left):
            if type(pattern) is Argument:
                return n, Argument(self.name, pattern.value)
        return None, None

else:
        argv ::= [ long | shorts | argument ]* [ '--' [ argument ]* ] ;

    """
    parsed = []
    while tokens.current() is not None:
        if tokens.current() == '--':
            return parsed + [Argument(None, v) for v in tokens]
        elif tokens.current().startswith('--'):
            parsed += parse_long(tokens, options)
        elif tokens.current().startswith('-') and tokens.current() != '-':
            parsed += parse_shorts(tokens, options)
        elif options_first:
            return parsed + [Argument(None, v) for v in tokens]
        else:
            parsed.append(Argument(None, tokens.move()))
    return parsed

class Argument(LeafPattern):

    def single_match(self, left):
        for n, pattern in enumerate(left):
            if type(pattern) is Argument:
                return n, Argument(self.name, pattern.value)
        return None, None

    @classmethod
    def parse(class_, source):
        name = re.findall('(<\S*?>)', source)[0]
        value = re.findall('\[default: (.*)\]', source, flags=re.I)
        return class_(name, value[0] if value else None)


class Command(Argument):

    def __init__(self, name, value=False):
        self.name, self.value = name, value

    def single_match(self, left):
        for n, pattern in enumerate(left):
            if type(pattern) is Argument:
                if pattern.value == self.name:
                    return n, Command(self.name, True)
                else:
                    break
        return None, None


class Option(LeafPattern):

If options_first:
        argv ::= [ long | shorts ]* [ argument ]* [ '--' [ argument ]* ] ;
    else:
        argv ::= [ long | shorts | argument ]* [ '--' [ argument ]* ] ;

    """
    parsed = []
    while tokens.current() is not None:
        if tokens.current() == '--':
            return parsed + [Argument(None, v) for v in tokens]
        elif tokens.current().startswith('--'):
            parsed += parse_long(tokens, options)
        elif tokens.current().startswith('-') and tokens.current() != '-':
            parsed += parse_shorts(tokens, options)
        elif options_first:
            return parsed + [Argument(None, v) for v in tokens]
        else:
            parsed.append(Argument(None, tokens.move()))
    return parsed

# group_arg contains members as dependency arguments
        options = arg.children[0].children
        p_node = self._getDependencyParentNode(ancestors)
        members = [self._generateDependencyArgument(option) for
                   option in options]

        pretty_names = [member["name"] for member in members]
        names = [arg.name for arg in arg.children[0].children]
        gdesc = "Group key for mutex choices: {0}".format(
            " and ".join(names))
        for name in [name for name in names if name in self.all_desc_and_type]:
            gdesc = gdesc.replace(name, "{0} ({1})".format(
                name, self.all_desc_and_type[name]['desc']
            ))
        gname = "<{0}>".format("_".join(pretty_names))
        grp_arg = Argument(gname)
        grp_arg.parse(gname)
        self.all_desc_and_type[gname] = {'desc': gdesc}

        self._addArgumentToDependencies(
            grp_arg, ancestors=ancestors,
            optional=optional, members=members)
        ancestors.append(grp_arg.name)
        return ancestors