code: final public StringWrapper prepare(String s) {
  		BagOfTokens bag = new BagOfTokens(s, tokenizer.tokenize(s));
  		double totalWeight = bag.getTotalWeight();
  		for (Iterator i=bag.tokenIterator(); i.hasNext(); ) {
  			Token tok = (Token)i.next();
  			double freq = bag.getWeight(tok);
  			bag.setWeight( tok, smoothedProbability(tok, freq, totalWeight) );
  		}
  		return bag;
  	}
docs: Preprocess a string by finding tokens and giving them weights W
  such that W is the smoothed probability of the token appearing
  in the document.