docs: public String classifyToString(String sentences, String outputFormat, boolean preserveSpacing) {
      PlainTextDocumentReaderAndWriter.OutputStyle outFormat =
        PlainTextDocumentReaderAndWriter.OutputStyle.fromShortName(outputFormat);
  
      
      ObjectBank<List<IN>> documents =
        makeObjectBankFromString(sentences, plainTextReaderAndWriter);
  
      StringBuilder sb = new StringBuilder();
      for (List<IN> doc : documents) {
        List<IN> docOutput = classify(doc);
        if (plainTextReaderAndWriter instanceof 
            PlainTextDocumentReaderAndWriter) {
          // TODO: implement this particular method and its options in
          // the other documentReaderAndWriters
          sb.append(((PlainTextDocumentReaderAndWriter) plainTextReaderAndWriter).getAnswers(docOutput, outFormat, preserveSpacing));
        } else {
          StringWriter sw = new StringWriter();
          PrintWriter pw = new PrintWriter(sw);
          plainTextReaderAndWriter.printAnswers(docOutput, pw);
          pw.flush();
          sb.append(sw.toString());
          sb.append("\n");
        }
      }
      return sb.toString();
    }