public static String serializeObject(Serializable expr) {
    return new String(Base64.encodeBase64(serializeObjectToKryo(expr)),
        StandardCharsets.UTF_8);
  }
Deserializes expression from Kryo.
@param bytes Bytes containing the expression.
@param isPartFilter ture if it is a partition filter
@return Expression; null if deserialization succeeded, but the result type is incorrect.
ql/src/java/org/apache/hadoop/hive/ql/exec/SerializationUtilities.java