Return a function object suitable for the "set" side of the attribute
        property descriptor.

def _setter(self):
        """
        Return a function object suitable for the "set" side of the attribute
        property descriptor.
        """
        def set_attr_value(obj, value):
            str_value = self._simple_type.to_xml(value)
            obj.set(self._clark_name, str_value)
        return set_attr_value