human
Solve the following python programming problem given the following code:
def _betavariate_impl(context, builder, sig, args, gamma) : 
    def betavariate_impl(alpha, beta) : 
        'Beta distribution.  Taken from CPython.
        ' 
        y = gamma (alpha, 1.0) 
        if (y == 0.0) : 
            return 0.0 
else : 
            return (y / (y + gamma (beta, 1.0))) 
return context.compile_internal (builder, <MASK>, sig, args) 
    
    Given the code above, what is a proper replacement for <MASK>?
assistant
#Here is a proper replacement for <MASK>.
def betavariate_impl(