declare class DelayedFetch implements PromiseLike<Response> {
    request: Request;
    fetchFunction: typeof fetch;
    innerPromise: Promise<Response> | null;
    constructor(delayedFunction: Promise<Response>);
    withHeader(key: string, value: string): this;
    then<TResult1 = Response, TResult2 = never>(onfulfilled?: ((value: Response) => TResult1 | PromiseLike<TResult1>) | undefined | null, onrejected?: ((reason: any) => TResult2 | PromiseLike<TResult2>) | undefined | null): PromiseLike<TResult1 | TResult2>;
    catch<TResult2 = never>(onrejected: ((reason: any) => TResult2 | PromiseLike<TResult2>) | undefined | null): PromiseLike<Response | TResult2>;
    private doInner;
}