lazy_doc.py

class WithLazyDoc:                                                                   
    def __init__(self, get_doc, f): 
        self._get_doc = get_doc 
        self._f = f 
      
    @property 
    def __wrapped__(self): 
        return self._f 
 
    @property 
    def __signature__(self): 
        return inspect.signature(self._f) 
 
    @property 
    def __doc__(self): 
        return self._get_doc() 
     
    def __call__(self, *args, **kwargs): 
        return self._f(*args, **kwargs)     
         

class C:
    def m(self, a, b):
        pass


def lazy_doc():
    lazy_doc.called += 1
    return f'lazy doc {lazy_doc.called}'
lazy_doc.called = 0


C.m = WithLazyDoc(lazy_doc, C.m)

terminal_session

In [23]: C.m?                                                                                  
Signature:      C.m(self, a, b)
Call signature: C.m(*args, **kwargs)
Type:           WithLazyDoc
String form:    <__main__.WithLazyDoc object at 0x7feb0c20ad90>
File:           ~/quantopian/qexec/<ipython-input-22-4a8288420109>
Docstring:      lazy doc 1

In [24]: C.m?                                                                                  
Signature:      C.m(self, a, b)
Call signature: C.m(*args, **kwargs)
Type:           WithLazyDoc
String form:    <__main__.WithLazyDoc object at 0x7feb0c20ad90>
File:           ~/quantopian/qexec/<ipython-input-22-4a8288420109>
Docstring:      lazy doc 2

In [25]: C.m?                                                                                  
Signature:      C.m(self, a, b)
Call signature: C.m(*args, **kwargs)
Type:           WithLazyDoc
String form:    <__main__.WithLazyDoc object at 0x7feb0c20ad90>
File:           ~/quantopian/qexec/<ipython-input-22-4a8288420109>
Docstring:      lazy doc 3