How to filter ID from Realm

I am trying to filter out a id from Realm object like this:

let itemsInCart = realm.objects("Cart").filtered("id = " + itemId);

My Cart schema is as follows:

export const CART_SCHEMA = "Cart";
export const CartSchema = {
  name: CART_SCHEMA,
  primaryKey: "id",
  properties: {
    id: "string",
    quantity: "int",
    productName: "string",
    productImage: "string"
  }
};

I want to check whether the id exists or not in my Cart object but whenever I try to filter out the id it gives the following error: