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

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