docs: 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