code: public final CellName clusteringKey(BytesRef bytesRef) {
          String string = bytesRef.utf8ToString();
          ByteBuffer bb = ByteBufferUtils.fromString(string);
          return cellNameType.cellFromByteBuffer(bb);
      }
docs: Returns the clustering key contained in the specified Lucene field value.
  
  @param bytesRef The {@link BytesRef} containing the raw clustering key to be get.
  @return The clustering key contained in the specified Lucene field value.