解除装饰器作用（python3新增）

一个装饰器已经作用在一个函数上，你想撤销它，直接访问原始的未包装的那个函数。

假设装饰器是通过 @wraps 来实现的，那么你可以通过访问 wrapped 属性来访问原始函数：

>>> @somedecorator
>>> def add(x, y):
...     return x + y
...
>>> orig_add = add.__wrapped__
>>> orig_add(3, 4)
7
>>>

如果有多个包装器：

In [588]: from functools import wraps

In [589]: def decorator1(func):
     ...:     @wraps(func)
     ...:     def wrapper(*args, **kwargs):
     ...:         print ('Decorator 1')
     ...:         return func(*args, **kwargs)
     ...:     return wrapper
     ...: 

In [590]: def decorator2(func):
     ...:     @wraps(func)
     ...:     def wrapper(*args, **kwargs):
     ...:         print ('Decorator 2')
     ...:         return func(*args, **kwargs)
     ...:     return wrapper
     ...: 

In [591]: @decorator1
     ...: @decorator2
     ...: def add(x, y):
     ...:     return x+y
     ...: 

In [592]: add(2,3)
Decorator 1
Decorator 2
Out[592]: 5

In [593]: add.__wrapped__(2, 3)
Decorator 2
Out[593]: 5

In [594]: add.__wrapped__.__wrapped__(2,3)
Out[594]: 5

参考：Python Cookbook