code: def save_token(self, access_token):
          
          self.write(access_token.token, access_token.__dict__)
  
          unique_token_key = self._unique_token_key(access_token.client_id,
                                                    access_token.grant_type,
                                                    access_token.user_id)
          self.write(unique_token_key, access_token.__dict__)
  
          if access_token.refresh_token is not None:
              self.write(access_token.refresh_token, access_token.__dict__)
docs: Stores the access token and additional data in redis.
  
          See :class:`oauth2.store.AccessTokenStore`.