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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 reference_id(self, reference_id):
 """ Sets the reference_id of this Order. A client specified identifier to associate an entity in another system with this order. :param reference_id: The reference_id of this Order. :type: str """


        if reference_id is None:
            raise ValueError("Invalid value for `reference_id`, must not be `None`")
        if len(reference_id) > 40:
            raise ValueError("Invalid value for `reference_id`, length must be less than `40`")

        self._reference_id = reference_id