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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 fetch_last_receipt_number(self, point_of_sales, receipt_type):
 """Returns the number for the last validated receipt."""

        client = clients.get_client('wsfe', point_of_sales.owner.is_sandboxed)
        response_xml = client.service.FECompUltimoAutorizado(
            serializers.serialize_ticket(
                point_of_sales.owner.get_or_create_ticket('wsfe')
            ),
            point_of_sales.number,
            receipt_type.code,
        )
        check_response(response_xml)

        # TODO XXX: Error handling
        # (FERecuperaLastCbteResponse){
        #    PtoVta = 0
        #    CbteTipo = 0
        #    CbteNro = 0
        #    Errors =
        #       (ArrayOfErr){
        #          Err[] =
        #             (Err){
        #                Code = 601
        #                Msg = "CUIT representada no incluida en Token"
        #             },
        #       }
        #  }

        return response_xml.CbteNro