def add(self, num_iid, properties, quantity, price, session, outer_id=None, item_price=None, lang=None):
        '''taobao.item.sku.add 添加SKU
        
        新增一个sku到num_iid指定的商品中 传入的iid所对应的商品必须属于当前会话的用户'''
        request = TOPRequest('taobao.item.sku.add')
        request['num_iid'] = num_iid
        request['properties'] = properties
        request['quantity'] = quantity
        request['price'] = price
        if outer_id!=None:
            request['outer_id'] = outer_id
        if item_price!=None:
            request['item_price'] = item_price
        if lang!=None:
            request['lang'] = lang
        self.create(self.execute(request, session)['sku'])
        return self