@Override
  public void writeExternal(ObjectOutput out) throws IOException {
    out.writeLong(serialVersionUID);
    writeType(type, out);
    type.proxyWrite(proxied, out);
  }
Called by serialization after readExternal.
@return the proxied instance
@throws IOException for signature compliance
standalone-metastore/metastore-common/src/main/java/org/apache/hadoop/hive/metastore/properties/SerializationProxy.java