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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 _generate_struct_class_slots(self, data_type):
 """Creates a slots declaration for struct classes. Slots are an optimization in Python. They reduce the memory footprint of instances since attributes cannot be added after declaration. """

        with self.block('__slots__ =', delim=('[', ']')):
            for field in data_type.fields:
                field_name = fmt_var(field.name)
                self.emit("'_%s_value'," % field_name)
                self.emit("'_%s_present'," % field_name)
        self.emit()