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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def register_structure_hook(self, cl, func):
 """Register a primitive-to-class converter function for a type. The converter function should take two arguments: * a Python object to be converted, * the type to convert to and return the instance of the class. The type may seem redundant, but is sometimes needed (for example, when dealing with generic classes). """

        if is_union_type(cl):
            self._union_registry[cl] = func
        else:
            self._structure_func.register_cls_list([(cl, func)])