code: def commit(self) -> None:
          
          now = datetime.now(timezone.utc)
          if self.first_commit_at is None:
              self.first_commit_at = now
  
          if self.mode == "r":
              response = self.engine.session.transaction_read(self._request)
          elif self.mode == "w":
              if now - self.first_commit_at > MAX_TOKEN_LIFETIME:
                  raise TransactionTokenExpired
              response = self.engine.session.transaction_write(self._request, self.tx_id)
          else:
              raise ValueError(f"unrecognized mode {self.mode}")
  
          self._handle_response(response)
docs: Commit the transaction with a fixed transaction id.
  
          A read transaction can call commit() any number of times, while a write transaction can only use the
          same tx_id for 10 minutes from the first call.