filters['invoice__user'] = user

        for item in LineItem.objects.filter(**filters).values('id', 'quantity'):

            yield (item['id'], list(create_ticket_numbers(item)))

    @property

    def locked(self):

        return self._locked

    def unlock(self, user):

        self.audit_events.create(user=user, reason="Unlocked")

        self._locked = False

    def remove_winner(self, user):

        reason = "Removed winning ticket: {}".format(self.winning_ticket.id)

        self.audit_events.create(user=user, reason=reason)

        self.winning_ticket = None

        self.save(update_fields=('winning_ticket',))

from django.db import models

class Raffle(RaffleMixin, models.Model):

    """

    Stores a single Raffle object, related to one or many

    :model:`pinaxcon_registrasion.Product`, which  is usually a raffle ticket,

    products = models.ManyToManyField('registrasion.Product')

    def __str__(self):

        return self.description

    """

    Stores a Prize for a given :model:`pinaxcon_raffle.Raffle`.

    Once `winning_ticket` has been set to a :model:`pinaxcon_raffle.DrawnTicket`

    object, no further changes are permitted unless the object is explicitely

    unlocked.

        ordering = ('-timestamp',)

    def __str__(self):

        return self.reason

    """

    Stores a draw for a given :model:`pinaxcon_raffle.Raffle`, along with audit fields

    for the creating :model:`auth.User` and the creation timestamp.

    """

    raffle = models.ForeignKey('pinaxcon_raffle.Raffle', related_name='draws')

    drawn_by = models.ForeignKey('auth.User')

    drawn_time = models.DateTimeField(auto_now_add=True)

    def __str__(self):

        return f"{self.raffle}: {self.drawn_time}"

    """

    Stores the result of a ticket draw, along with the corresponding

    :model:`pinaxcon_raffle.Draw`, :model:`pinaxcon_raffle.Prize` and the

    :model:`registrasion.commerce.LineItem` from which it was generated.

    """

    ticket = models.CharField(max_length=255)