code: def doRollback(self):
      '''
      Call each rollback step in LIFO order.
      '''
      while self.steps:
        callback, args, kwargs = self.steps.pop()
        callback(*args, **kwargsf doRollback(self):
      '''
      Call each rollback step in LIFO order.
      '''
      while self.steps:
        callback, args, kwargs = self.steps.pop()
        callback(*args, **kwargs)
docs: Call each rollback step in LIFO order.