code: function TransformStreamCloseReadable(transformStream) {
    // console.log('TransformStreamCloseReadable()');
  
    if (transformStream._errored === true) {
      throw new TypeError('TransformStream is already errored');
    }
  
    if (transformStream._readableClosed === true) {
      throw new TypeError('Readable side is already closed');
    }
  
    TransformStreamCloseReadableInternal(transformStream);
  }
docs: Methods on the transform stream controller object