code: function transform(transform, flush) {
    const stream = new Transform({ objectMode: true });
    stream._transform = transform;
    if (typeof flush === 'function') {
      stream._flush = flush;
    }
    return stream;
  }
docs: Convenience function for creating a Transform stream
  
  @param {Function} transform - A function to be called for each File received
  @param {Function} [flush] - A function to be called when the stream ends
  @returns {external:stream.Transform}