Add item in zoho books from zoho crm

Hi,

i am trying to add item just below in the existing item from zoho crm into zoho books.

i tried this code as below:

opportunityRecord = zoho.crm.getRecordById("Deals",dealID);

upgrade_program = opportunityRecord.get("Upgrade_Program");

//info upgrade_program;

productID = upgrade_program.get("id");

productRecord = zoho.crm.getRecordById("Products",productID);

unit_price = productRecord.get("Unit_Price");

//info unit_price;

mp = Map();

mp.put("Upgrade_Program_Price",unit_price);

//mp.put("Upgrade_Invoice_Updated",true);

// updateRecord = zoho.crm.updateRecord("Deals",dealID,mp);

//info updateRecord;

////////

//add the same product in the z-Books

invoiceID = opportunityRecord.get("Books_Invoice_Id");

info invoiceID;

product_name = productRecord.get("Product_Name");

description = productRecord.get("Descriptioin");

itemList = List();

item1 = Map();

item1.put("item_id",invoiceID);

item1.put("rate",unit_price);

item1.put("quantity",1);

itemList.add(item1);

info itemList;

invoiceMap = Map();

invoiceMap.put("line_items",itemList);

response = zoho.books.updateRecord("Invoices",invoiceID,invoiceMap,"crm_to_books");

info response;

but i am getting error as ,

Failed to execute function

Argument type mismatch - Found 'TEXT' but Expected '[MAP]' for the function '519' Line Number:106