export interface Observer<T> {
    /**
     * Creates observer of event.
     * @param {Function[]} subscribers - callback of subscribers.
     */
    new(subscribers: Array<(message: T) => void>);

    /**
     * Adds method of subscriber for notification.
     * @param {Function} callback - the method of notification, this method can be declared, when observer was notified.
     */
    subscribe (callback: (message: T) => void);

    /**
     * Removes method of subscriber.
     * @param {Function} callback - the method of notification.
     */
    unsubscribe (callback: (message: T) => void);
}