class CreatePurchase(Wizard):
    'Create Purchase'
    __name__ = 'purchase.request.create_purchase'

    @classmethod
    def _group_purchase_key(self, requests, request):
        pool = Pool()
        Date = pool.get('ir.date')

        key = super(CreatePurchase, self)._group_purchase_key(
            requests, request)
        key += (
            ('shipping_mode', request.shipping_mode.id
                if request.shipping_mode else None),
            ('incoterm', request.party.incoterm),
            ('incoterm_place', request.party.incoterm_place),
            ('purchase_date', Date.today()),
            ('delivery_date', request.supply_date),
            )
        return key