code: def parse_pseudo_open(self, sel, name, has_selector, iselector, index):
          
  
          flags = FLG_PSEUDO | FLG_OPEN
          if name == ':not':
              flags |= FLG_NOT
          if name == ':has':
              flags |= FLG_RELATIVE
  
          sel.selectors.append(self.parse_selectors(iselector, index, flags))
          has_selector = True
          return has_selector
docs: Parse pseudo with opening bracket.