protected String getConstantStringValue(ObjectInspector[] arguments, int i) {
    Object constValue = ((ConstantObjectInspector) arguments[i]).getWritableConstantValue();
    String str = constValue == null ? null : constValue.toString();
    return str;
  }
Some information may be set during initialize() which needs to be saved when the UDF is copied.
This will be called by FunctionRegistry.cloneGenericUDF()
ql/src/java/org/apache/hadoop/hive/ql/udf/generic/GenericUDF.java