I'm trying to create the application in this  Example 2, but using the code given returns error

Error at line number : 8 
Field 'Product_Details' is of type subform and is not supported in update expression

The given code as shown below;

quoteDetails = map(); 
quoteDetails.put("Subject", input.Subject); 
quoteDetails.put("ACCOUNTID", input.Account_ID); 
productsList = List:Map(); 
 
for each product in input.Product_Details 
{ 
Product_Details = map(); 
Product_Details.put("Product Id", product.Product_ID); 
Product_Details.put("Quantity", product.Quantity); 
productsList.add(productDetails); 
} 
quoteDetails.put("Products", productsList); 

response = zoho.crm.updateRecord("Quotes", QuotesID, quoteDetails);

Anyone can help please, thanks.