@Override
  public ObjectInspector initialize(ObjectInspector[] arguments) throws UDFArgumentException {
    throw new UDFArgumentException("GenericUDFStructField shouldn't be used directly.");
  }
The class shouldn't be used, and only to align the implementation of vectorization UDF for
struct field.
ql/src/java/org/apache/hadoop/hive/ql/udf/generic/GenericUDFStructField.java