docs: function parse(input, fn) {
    let returnValue;
    const transformed = transformPair(input, (readable, writable) => {
      const reader = getReader(readable);
      reader.remainder = () => {
        reader.releaseLock();
        pipe(readable, writable);
        return transformed;
      };
      returnValue = fn(reader);
    });
    return returnValue;
  }