'Returns the unit price to store on the quant'

@api.multi
def get_price_unit(self):

    if self.purchase_line_id:
        order = self.purchase_line_id.order_id
        if (order.currency_id != self.company_id.currency_id):
            price_unit = self.purchase_line_id._get_stock_move_price_unit()
            self.write({'price_unit': price_unit})
            return price_unit
        return self.price_unit
    return super(StockMove, self).get_price_unit()
