If you've already pickled instances of a class that needs changing, you'll likely want to retrieve and update those instances so that they continue to function properly with the new class definition.

如果已经对某个类实例进行了pickle，而现在又需要更改这个类，则您可能要检索和更新那些实例，以便它们能在新的类定义下继续正常工作。