@Nullable
  static Pair<ZstdDictDecompress, Integer> getDecompressDictionary(final Configuration conf) {
    String path = conf.get(ZSTD_DICTIONARY_KEY);
    if (path == null) {
      return null;
    }

    try {
      return DECOMPRESS_DICT_CACHE.get(path, () -> {
        byte[] dictBytes = DictionaryCache.getDictionary(conf, path);
        int dictId = getDictionaryId(dictBytes);
        return new Pair<>(new ZstdDictDecompress(dictBytes), dictId);
      });
    } catch (ExecutionException e) {
      throw new RuntimeException("Unable to load ZSTD dictionary", e);
    }
  }
Returns dictionary and its ID number, useful for comparing to other dictionaries for equality
hbase-compression/hbase-compression-zstd/src/main/java/org/apache/hadoop/hbase/io/compress/zstd/ZstdCodec.java