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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 validate(self, ticket=None, raise_=False):
 """ Validates this receipt. This is a shortcut to :class:`~.ReceiptQuerySet`'s method of the same name. Calling this validates only this instance. :param AuthTicket ticket: Use this ticket. If None, one will be loaded or created automatically. :param bool raise_: If True, an exception will be raised when validation fails. """

        # XXX: Maybe actually have this sortcut raise an exception?
        rv = Receipt.objects.filter(pk=self.pk).validate(ticket)
        # Since we're operating via a queryset, this instance isn't properly
        # updated:
        self.refresh_from_db()
        if raise_ and rv:
            raise exceptions.ValidationError(rv[0])
        return rv