code: private String loadExistingMetadata(Path metadataFilename, int branchId) {
      try {
        FileSystem fsForBranch = writerFileSystemByBranches.get(branchId);
        if (!fsForBranch.exists(metadataFilename)) {
          return null;
        }
        FSDataInputStream existingMetadata = writerFileSystemByBranches.get(branchId).open(metadataFilename);
        return IOUtils.toString(existingMetadata, StandardCharsets.UTF_8);
      } catch (IOException e) {
        LOG.warn("IOException {} while trying to read existing metadata {} - treating as null", e.getMessage(),
            metadataFilename.toString());
        return null;
      }
    }
docs: Read in existing metadata as a UTF8 string.