code: public DocumentReaderAndWriter<IN> makePlainTextReaderAndWriter() {
      String readerClassName = flags.plainTextDocumentReaderAndWriter;
      // We set this default here if needed because there may be models
      // which don't have the reader flag set
      if (readerClassName == null) {
        readerClassName = SeqClassifierFlags.DEFAULT_PLAIN_TEXT_READER;
      }
      DocumentReaderAndWriter<IN> readerAndWriter;
      try {
        readerAndWriter = ((DocumentReaderAndWriter<IN>) Class.forName(readerClassName).newInstance());
      } catch (Exception e) {
        throw new RuntimeException(String.format("Error loading flags.plainTextDocumentReaderAndWriter: '%s'", flags.plainTextDocumentReaderAndWriter), e);
      }
      readerAndWriter.init(flags);
      return readerAndWriter;
    }
docs: Makes a DocumentReaderAndWriter based on
  flags.plainTextReaderAndWriter.  Useful for reading in
  untokenized text documents or reading plain text from the command
  line.  An example of a way to use this would be to return a
  edu.stanford.nlp.wordseg.Sighan2005DocumentReaderAndWriter for
  the Chinese Segmenter.