Python对象包装器

我正在尝试创建一个行为类似于包装对象的包装类.到目前为止,我已经提出以下代码:

import functools
import types

method_wrapper = type((None).__str__)

class Box:

    def __new__(cls, obj):
        attrs = {}
        attr_names = dir(obj)

        for attr_name in attr_names:
            attr = obj.__getattribute__(attr_name)

            if isinstance(attr, (types.MethodType, method_wrapper)):
                "Attr is a bound method, ignore self"
                @functools.wraps(attr)
                def wrapped_attr(self, *args, **kwargs):
                    return attr(*args, **kwargs)
                attrs[attr_name] = wrapped_attr

            elif isinstance(attr, types.FunctionType):
                "attr is a static method"
                attrs[attr_name] = staticmethod(attr)

            else:
                "attr is a property"
                attrs[attr_name] = attr

        cls = type(type(obj).__name__,
                   (cls, type(obj)),
                   attrs)

        return object.__new__(cls)

我试过测试它:

if __name__ == '__main__':
    x=Box(object())

但是它会出现以下错误消息:

TypeError: __init__() should return None, not 'NotImplementedType'

__init__被正确派遣isinstance(attr, (types.MethodType, method_wrapper)),wrapped_attr似乎被执行.你知道为什么会这样吗？