def payment_event_quantity(self, event_type):
        result = self.payment_event_quantities.filter(
            event__event_type=event_type).aggregate(Sum('quantity'))
        if result['quantity__sum'] is None:
            return 0
        else:
            return result['quantity__sum']
Return the quantity of this line that has been involved in a payment
dataset/ETHPy150Open django-oscar/django-oscar/src/oscar/apps/order/abstract_models.py/AbstractLine.payment_event_quantity