code: public String strLabeling(File file){
  		List<Sentence> obsvSeqs = dataReader.readFile(file.getPath());
  		List lblSeqs = labeling(obsvSeqs);
  		String ret = dataWriter.writeString(lblSeqs);
  		return ret;
  	}
docs: labeling observation sequences.
  
  @param file contains a list of observation sequence, this file has a format wich can be read by DataReader
  @return string representing label sequences, the format is specified by writer