How to set and get Telegram Web App CloudStorage key value?

Can anyone explain how to?

const student = JSON.stringify(Telegram.WebApp.initDataUnsafe);
const key = 'user_data';
Telegram.WebApp.CloudStorage.setItem(key, student, (error, success) => {
               if (error) {
                   alert('Error storing JSON string:', error);
               } else if (success) {
                   alert('JSON string stored successfully');

   Telegram.WebApp.CloudStorage.getItem(key, (error, value) => {
        if (error) {
            alert('Error retrieving JSON string:', error);
                    } else {
            alert('Retrieved JSON string:', value);
        }
    });
        }
        });

Did it according to https://core.telegram.org/bots/webapps#cloudstorage
but receive empty value and no errors every attempt. Shall I init CloudStorage on a server side?