code: def freeze(self):
          
  
          if self.no_match:
              return ct.SelectorNull()
          else:
              return ct.Selector(
                  self.tag,
                  tuple(self.ids),
                  tuple(self.classes),
                  tuple(self.attributes),
                  tuple(self.nth),
                  tuple(self.selectors),
                  self._freeze_relations(self.relations),
                  self.rel_type,
                  tuple(self.contains),
                  tuple(self.lang),
                  self.flags
              )
docs: Freeze self.