code: public static String get(String fromWord, String fromPos, String toWord, String toPos)
      {
          String dependency = get(fromWord + "@" + toWord);
          if (dependency == null) dependency = get(fromWord + "@" + WordNatureWeightModelMaker.wrapTag(toPos));
          if (dependency == null) dependency = get(WordNatureWeightModelMaker.wrapTag(fromPos) + "@" + toWord);
          if (dependency == null) dependency = get(WordNatureWeightModelMaker.wrapTag(fromPos) + "@" + WordNatureWeightModelMaker.wrapTag(toPos));
          if (dependency == null) dependency = "未知";
  
          return dependency;
      }
docs: 获取一个词和另一个词最可能的依存关系
  @param fromWord
  @param fromPos
  @param toWord
  @param toPos
  @return