vectorizer = CountVectorizer() #构建一个计算词频（TF）的玩意儿，当然这里面不足是可以做这些
transformer = TfidfTransformer() #构建一个计算TF-IDF的玩意儿
TfidfTransformer + CountVectorizer = TfidfVectorizer
Python中的TfidfVectorizer参数解析：https://blog.csdn.net/feng_zhiyu/article/details/81952697
TF-IDF算法介绍及实现：https://blog.csdn.net/asialee_bird/article/details/81486700
