code: void transduce_instance_to_dependency(final Instance data,
                                            Dependency dependency, boolean with_dependencies)
      {
          int L = data.forms.size();
          for (int i = 0; i < L; ++i)
          {
              Integer form = forms_alphabet.idOf(data.forms.get(i));
              if (form == null)
              {
                  form = forms_alphabet.idOf(SpecialOption.UNKNOWN);
              }
              Integer postag = postags_alphabet.idOf(data.postags.get(i));
              if (postag == null) postag = postags_alphabet.idOf(SpecialOption.UNKNOWN);
              int deprel = (with_dependencies ? deprels_alphabet.idOf(data.deprels.get(i)) : -1);
  
              dependency.forms.add(form);
              dependency.postags.add(postag);
              dependency.heads.add(with_dependencies ? data.heads.get(i) : -1);
              dependency.deprels.add(with_dependencies ? deprel : -1);
          }
      }
docs: 将实例转为依存树
  @param data 实例
  @param dependency 输出的依存树
  @param with_dependencies 是否输出依存关系（仅在解析后才有意义）