How to use the muffin.urls.Traverser function in muffin

def state_max_repeat(self, value):
        """Parse repeatable parts."""
        min_, max_, value = value
        value = [val for val in Traverser(value, self.groups)]
        if not min_ and max_:
            for val in value:
                if isinstance(val, required):
                    min_ = 1
                    break

        for val in value * min_:
            yield val

def state_in(self, value):
        """Parse ranges."""
        value = [val for val in Traverser(value, self.groups)]
        if not value or not value[0]:
            for val in self.literals - set(value):
                return (yield val)
        yield value[0]

def state_subpattern(self, value):
        """Parse subpatterns."""
        num, *_, parsed = value
        if num in self.groups:
            return (yield required(self.groups[num]))

        yield from Traverser(parsed, groups=self.groups)

def url(self, *subgroups, query=None, **groups):
        """Build URL."""
        parsed = re.sre_parse.parse(self._pattern.pattern)
        subgroups = {n:str(v) for n, v in enumerate(subgroups, 1)}
        groups_ = dict(parsed.pattern.groupdict)
        subgroups.update({
            groups_[k0]: str(v0)
            for k0, v0 in groups.items()
            if k0 in groups_
        })
        url = ''.join(str(val) for val in Traverser(parsed, subgroups))
        return self._append_query(url, query)