End date of line period MUST be within invoice period.
ubl-invoice:Invoice[cac:InvoicePeriod/cbc:EndDate]/cac:InvoiceLine/cac:InvoicePeriod/cbc:EndDate | ubl-creditnote:CreditNote[cac:InvoicePeriod/cbc:EndDate]/cac:CreditNoteLine/cac:InvoicePeriod/cbc:EndDate
xs:date(text()) <= xs:date(../../../cac:InvoicePeriod/cbc:EndDate)