GooglePlaylist importPlaylist(GooglePlaylist playlist, String playlistId)
      throws IOException, InvalidTokenException, PermissionDeniedException {
    ImportPlaylistRequest importPlaylistRequest = new ImportPlaylistRequest(playlist, playlistId);
    Map<String, Object> importPlaylistMap = createJsonMap(importPlaylistRequest);
    Map<String, String> params = new LinkedHashMap<>();
    HttpContent content = new JsonHttpContent(jsonFactory, importPlaylistMap);

    return makePostRequest(BASE_URL + "playlists/" + playlistId + ":import", Optional.of(params),
        content,
        GooglePlaylist.class);
  }
GoogleMusicHttpApi makes HTTP requests to read and write to the public Google Music's "Music
Library" APIs, following its documentation at
https://developers.google.com/youtube/mediaconnect.

<p>Note that this is the lowest level of Google Music interaction - that is, you probably don't
want to use this class and are better off using something like a bit higher level like the Google
Music DTP Exporter and Importer instead.
extensions/data-transfer/portability-data-transfer-google/src/main/java/org/datatransferproject/datatransfer/google/music/GoogleMusicHttpApi.java