private Collection<MediaAlbum> mergeAlbums(Collection<PhotoAlbum> a1,
      Collection<VideoAlbum> a2) {
    return Stream.concat(
        a1.stream().map(MediaAlbum::photoToMediaAlbum),
        a2.stream().map(MediaAlbum::videoToMediaAlbum)
    ).distinct().collect(Collectors.toList());
  }
Allows using existing Photo and Video adapters to create a Media adapter.
portability-spi-transfer/src/main/java/org/datatransferproject/spi/transfer/provider/converter/MediaExporterDecorator.java