export type MaybePromise<T> = T | Promise<T>;
export declare function isPromise<T>(value: MaybePromise<T>): value is Promise<T>;
export declare function chain<T, U = void>(valueOrPromise: MaybePromise<T>, onFulfilled: (value: T) => MaybePromise<U>, onRejected?: (reason: any) => MaybePromise<U>): MaybePromise<U>;
export declare function chainForEach<T>(values: Iterator<T>, callback: (value: T) => MaybePromise<void>): MaybePromise<void>;