code: public Map<String, Float> getTermAndRank(String content, int size)
      {
          Map<String, Float> map = getTermAndRank(content);
          Map<String, Float> result = top(size, map);
  
          return result;
      }
docs: 返回分数最高的前size个分词结果和对应的rank
  
  @param content
  @param size
  @return