code: def rollback(self):
          
          try:
              # No need to use the response it contains nothing.
              self._client._datastore_api.rollback(self.project, self._id)
          finally:
              super(Transaction, self).rollback()
              # Clear our own ID in case this gets accidentally reused.
              self._id = None
docs: Rolls back the current transaction.
  
          This method has necessary side-effects:
  
          - Sets the current transaction's ID to None.