code: public Collection<String> wordsNearestSum(Collection<String> positive, Collection<String> negative, int top) {
          return modelUtils.wordsNearestSum(positive, negative, top);
      }
docs: Words nearest based on positive and negative words
  @param positive the positive words
  @param negative the negative words
  @param top the top n words
  @return the words nearest the mean of the words