/** pipe upstream through a transform stream */
export declare const throughs: {
    <T>(stream?: TransformStream<T, T>): TransformStream<T, T>;
    <T, R>(stream: TransformStream<T, R>): TransformStream<T, R>;
    <T, R>(fn: (s: ReadableStream<T>) => ReadableStream<R>): TransformStream<T, R>;
};