Wrap a ReadableStream in a TransformStream.
var from = ;var concat = ;var toThrough = ;var readable = ;// Can be used as a Readable or Transformvar maybeTransform = ;;
readableStream as the only argument and returns a
through2 stream. If the returned stream is piped before
nextTick, the wrapped
readableStream will not flow until the upstream is flushed. If the stream is not piped before
nextTick, it is ended and flushed (acting as a proper readable).