What is incorrect about this syntax to set salesorder status to "pending_approval"

What is incorrect about this syntax to set salesorder status to "pending_approval"


  2. order_data = map();
  3. order_data.put("salesorder",{"status":"pending_approval"});
  4. sales_order_data = zoho.books.updateRecord("salesorders",books_organization_ID,sales_order_id, order_data);