code: def url_for(self, *subgroups, **groups):
          
          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_
          })
          path = ''.join(str(val) for val in Traverser(parsed, subgroups))
          return URL.build(path=path, encoded=True)
docs: Build URL.