code: def match(self, selector, index):
          
  
          pseudo = None
          m = self.re_pseudo_name.match(selector, index)
          if m:
              name = util.lower(css_unescape(m.group('name')))
              pattern = self.patterns.get(name)
              if pattern:
                  pseudo = pattern.match(selector, index)
                  if pseudo:
                      self.matched_name = pattern
  
          return pseudo
docs: Match the selector.