code: public static void insert(String key, String keyword, String nature, int freq) {
          Forest dic = get(key);
          String[] paramers = new String[2];
          paramers[0] = nature;
          paramers[1] = String.valueOf(freq);
          Value value = new Value(keyword, paramers);
          Library.insertWord(dic, value);
      }
docs: 关键词增加
  
  @param keyword 所要增加的关键词
  @param nature 关键词的词性
  @param freq 关键词的词频