export declare class ObserverManager<T> {
    /** Observes language changing events. */
    private observers;
    constructor();
    /** Adds an observer whose the specified key. */
    addObserver(key: string, observer: T): boolean;
    /** Removes an observer whose the specified key. */
    removeObserver(key: string): boolean;
    dispatch(callback: (observer: T) => void): void;
}