code: public /*@Nullable*/Downloader startGetThumbnail(
              DbxThumbnailSize sizeBound, DbxThumbnailFormat format, String path, /*@Nullable*/String rev)
          throws DbxException
      {
          DbxPathV1.checkArgNonRoot("path", path);
          if (sizeBound == null) throw new IllegalArgumentException("'size' can't be null");
          if (format == null) throw new IllegalArgumentException("'format' can't be null");
  
          String apiPath = "1/thumbnails/auto" + path;
          /*@Nullable*/String[] params = {
              "size", sizeBound.ident,
              "format", format.ident,
              "rev", rev,
          };
  
          return startGetSomething(apiPath, params);
      }
docs: Similar to {@link #getThumbnail}, except the thumbnail contents are returned via
  a {@link Downloader}.