human
Solve the following python programming problem given the following code:
def next_extractor(node) : 
    def selectNextBuiltinClass(iterator, default, source_ref) : 
        if (default is None) : 
            return ExpressionBuiltinNext1 (value = iterator, source_ref = source_ref) 
else : 
            return ExpressionBuiltinNext2 (iterator = iterator, default = default, source_ref = source_ref) 
return BuiltinOptimization.extractBuiltinArgs (node = node, builtin_class = <MASK>, builtin_spec = BuiltinOptimization.builtin_iter_spec) 
    
    Given the code above, what is a proper replacement for <MASK>?
assistant
#Here is a proper replacement for <MASK>.
def selectNextBuiltinClass(