anchor.diff:          /// cart.LineItems.AddOrUpdate(product, selectedOptions, 3);
           /// \endcode
           public void AddOrUpdate(Product product, Dictionary<string, string> selectedOptions, long? quantity = null, Dictionary<string, string> customAttributes = null) {
  -            string variantId = VariantIdFromSelectedOptions(product, selectedOptions);
  +            string variantId = VariantFromSelectedOptions(product, selectedOptions).id();
   
               if (variantId == null) {
                   throw new NoMatchingVariantException("Could not `AddOrUpdate` line item as no matching variant could be found for selected options");
  
positive.code:         /// Debug.Log(cart.LineItems.Get(product, selectedOptions).quantity);
          /// \endcode
          public CartLineItem Get(Product product, Dictionary<string, string> selectedOptions) {
              string variantId = VariantIdFromSelectedOptions(product, selectedOptions);
  
              if (variantId == null) {
                  return null;
  
negative.code:         private long _Quantity;
          private ObservableDictionary<string, string> _CustomAttributes;
          private OnCartLineItemChange OnChange;
  
          public CartLineItem(string variantId, OnCartLineItemChange onChange, long quantity = 1, IDictionary<string, string> customAttributes = null) {
              _VariantId = variantId;
              _Quantity = quantity;
  