export declare class PersistentStorageV2<T> {
    private storageKey;
    private expirationTime;
    private notifier;
    private subscription;
    constructor(storageKey: string, expirationTime: number);
    /**
     * Function to setup the persistent storage, only needed if you want/can retrieve the data,
     * if you only want to subscribe, call PersistentStorage.subscribe() instead and you will be
     * notified of changes on that data.
     *
     * @param callback Function to retrieve the data to be persisted on cache
     * @param expirationTime Persistance duration for the data retrieved by the callback, by default will use the one provided on the constructor.
     */
    setup(callback: Function, expirationTime?: number): Promise<void>;
    get(): T;
    private getFromStorage;
    private getExpirationTime;
    set(data: T, expirationTime?: number): void;
    /**
     * You will be subscribed to data changes for this persistent storage,
     * only one subscription is allowed, for multiple subscriptions to the same key,
     * you will need multiple instances.
     *
     * @param callback Function to be called on cached data change.
     */
    subscribe(callback: Function): void;
    /**
     * Call this for cleanup purposes, to clean up the subscription and avoid memory leaks.
     */
    unsubscribe(): void;
}