code: def copy(self):
          
          new = self.__class__()
          for dict_attr in ("symbol2number", "number2symbol", "dfas", "keywords",
                            "tokens", "symbol2label"):
              setattr(new, dict_attr, getattr(self, dict_attr).copy())
          new.labels = self.labels[:]
          new.states = self.states[:]
          new.start = self.start
          return new
docs: Copy the grammar.