if (typeof (notebook) === "string") {
            console.warn("[notebook_model.ts] (╯°□°）╯︵ ┻━┻ :: Apparently Notebook has been serialized twice, deserializing a second time !");
            // here we need to cast notebook to <any> as otherwise compiler complain
            // that string/ notebook cannot be cast to each other.
            notebook = JSON.parse(notebook);
            console.warn("[notebook_model.ts] Double desirializing went ok.");
        }