def is_validated(self):
        """
        Returns True if this instance is validated.

        Note that resolving this property requires a DB query, so if you've a
        very large amount of receipts you should prefetch (see django's
        ``select_related``) the ``validation`` field. Even so, a DB query *may*
        be triggered.

        If you need a large list of validated receipts, you should actually
        filter them via a QuerySet::

            Receipt.objects.filter(validation__result==RESULT_APPROVED)

        :rtype: bool
        """
        # Avoid the DB lookup if possible:
        if not self.receipt_number:
            return False

        try:
            return self.validation.result == ReceiptValidation.RESULT_APPROVED
        except ReceiptValidation.DoesNotExist:
            return False
Returns True if this instance is validated.

        Note that resolving this property requires a DB query, so if you've a
        very large amount of receipts you should prefetch (see django's
        ``select_related``) the ``validation`` field. Even so, a DB query *may*
        be triggered.

        If you need a large list of validated receipts, you should actually
        filter them via a QuerySet::

            Receipt.objects.filter(validation__result==RESULT_APPROVED)

        :rtype: bool