docs: function(file) {
      return fs.openAsync(file, 'r').then((fileDescriptor) => {
        return lzma.parseFileIndexFDAsync(fileDescriptor).tap(() => {
          return fs.closeAsync(fileDescriptor);
        });
      }).then((metadata) => {
        return {
          stream: fs.createReadStream(file)
            .pipe(lzma.createDecompressor()),
          size: metadata.uncompressedSize,
          transform: new PassThroughStream()
        };
      });
    }