export declare const tokenSentToServer: (token: string) => boolean;
export declare const setTokenSentToServer: (token: string) => void;
export declare const subscribeToNotifications: (token: string) => void;
export declare const unsubscribeFromNotifications: () => Promise<void>;
/**
 * Checks to see if the required APIs for FCM exist as implemented in:
 * https://github.com/firebase/firebase-js-sdk/blob/master/packages/messaging/index.ts
 */
export declare const fcmIsSupported: () => boolean;