docs: public Set<String> getUniqueWords(Object document) {
          Set<String> features = new FastSet<String>();
  		if (document instanceof AnalyzedText){
  	        features.addAll(((AnalyzedText)document).getUniqueWords());
  		    if (includeLengthCategory){
  		       	features.add(((AnalyzedText)document).getLengthCategory().toString());
  		    }
  		}else{
  	        addWords(document, features);
  		}
  	    return features;
  	}