Variable ReadableStream

ReadableStream: {
    prototype: ReadableStream<any>;
    new (underlyingSource: UnderlyingByteSource, strategy?: {
        highWaterMark?: number;
    }): ReadableStream<Uint8Array>;
    new <R>(underlyingSource: UnderlyingDefaultSource<R>, strategy?: QueuingStrategy<R>): ReadableStream<R>;
    new <R>(underlyingSource?: UnderlyingSource<R>, strategy?: QueuingStrategy<R>): ReadableStream<R>;
}