code: function (basketItem, element, quantity, cb) {
                  this.extendElementWithLinks(element);
  
                  basketItem.set({
                      element: element,
                      quantity: quantity
                  });
  
                  basketItem.save(null, cb);
              }
docs: Updates the given basket item
  
  @param {sprd.model.BasketItem} basketItem
  @param {sprd.model.ConcreteElement} element
  @param {Number} quantity
  @param {Function} cb