human
Solve the following python programming problem given the following code:
def generator_factory(mother_class) : 
    def generator_progress(iteritem, iterations = None, * args, **kw) : 
        if (iterations is None) : 
            iterations = len (iteritem) 
assert iterations 
        mbar = mother_class (iterations, * args, ** kw) 
        for item in iteritem : 
            (yield item) 
            mbar.update () 
return <MASK> 
    
    Given the code above, what is a proper replacement for <MASK>?
assistant
#Here is a proper replacement for <MASK>.
def generator_progress(