code: @Override
    @SuppressWarnings("unchecked")
    public void prepareToRead(RecordReader reader, PigSplit split) {
      this.reader = (LuceneIndexRecordReader<T>) reader;
    }
docs: THIS INVOLVES AN UNCHECKED CAST
  Pig gives us a raw type for the RecordReader unfortunately.
  However, because {@link #getInputFormat()} is final and delegates
  to {@link #getLuceneIndexInputFormat()} we can be reasonably sure
  that this record reader is actually a LuceneIndexRecordReader<T>