@api.multi
@api.constrains('registration_ids', 'seats_max')
def _check_seats_limit(self):
    for record in self:
        if (record.seats_max and (record.seats_available < 0)):
            raise ValidationError(_('No more available seats for this ticket type.'))
@api.multi
@api.constrains('registration_ids', 'seats_max')
def _check_seats_limit(self):
    for record in self:
        if (record.seats_max and (record.seats_available < 0)):
            raise ValidationError(_('No more available seats for this ticket type.'))