自然语言处理：中文分词，打标签，文章匹配相似度
打标签： extra_tags.py：
关键函数：extarct_tags ，通过help(jieba.analyse.extarct_tags) 查看
函数提示如下：
withWeight：单词权重
allowPOS：单词性质，参看https://wenku.baidu.com/view/49eab3a9ad51f01dc281f1f8.html
withFlag：
======================================================
Help on method extract_tags in module jieba.analyse.tfidf:
extract_tags(self, sentence, topK=20, withWeight=False, allowPOS=(), withFlag=False) method of jieba.analyse.tfidf.TFIDF instance
Extract keywords from sentence using TF-IDF algorithm.
Parameter:
- topK: return how many top keywords. `None` for all possible words.
- withWeight: if True, return a list of (word, weight);
if False, return a list of words.
- allowPOS: the allowed POS list eg. ['ns', 'n', 'vn', 'v','nr'].
if the POS of w is not in this list,it will be filtered.
- withFlag: only work with allowPOS is not empty.
if True, return a list of pair(word, weight) like posseg.cut
if False, return a list of words