Class decorator with argument

[mk]

Hello,

I wrote this class decorator with argument:

 >>> class ChangeDoc(object):
	def __init__(self, docstring):
		self.docstring = docstring
	def __call__(self, func):
		func.__doc__ = self.docstring
		return func

It seems to work:

 >>> @ChangeDoc("bulba")
def f():
	pass

 >>> f.__doc__
'bulba'

Can someone please debug my reasoning if it's incorrect?

1. First, the decorator @ChangeDoc('bulba') instantiates with 
__init__(self, 'bulba'), to some class instance, let's call it _decor.

2. Then _decor's __call__ method is called with function f as argument, 
changing the docstring and returning the changed f object, like f = 
_decor(f) .

Am I missing smth important / potentially useful in typical real-world 
applications in that picture?

Regards,
mk