code: public DocumentReaderAndWriter<IN> makeReaderAndWriter() {
      DocumentReaderAndWriter<IN> readerAndWriter;
      try {
        readerAndWriter = ((DocumentReaderAndWriter<IN>)
                           Class.forName(flags.readerAndWriter).newInstance());
      } catch (Exception e) {
        throw new RuntimeException(String.format("Error loading flags.readerAndWriter: '%s'", flags.readerAndWriter), e);
      }
      readerAndWriter.init(flags);
      return readerAndWriter;
    }
docs: Makes a DocumentReaderAndWriter based on the flags the CRFClassifier
  was constructed with.  Will create the flags.readerAndWriter and
  initialize it with the CRFClassifier's flags.