def validate_order_currencies(order):
    """Check whether order contains more than one or an invalid currency"""
    currencies = set(order.items.values_list('currency', flat=True))
    if (currencies
            and (len(currencies) > 1 or currencies not in order.currency)):
        raise ValidationError(
            _('Order contains more than one currency.'),
            code='multiple_currency')
dataset/ETHPy150Open matthiask/plata/plata/shop/models.py/validate_order_currencies/swapped operands of `not in`