中文说明：此代码实现了TF-IDF 文本表示，为一个子函数，直接输入参数就可以调用运行，输入参数据两个：文本内容和特征词。输出可得到每个特征词下对应的权重。
English Description：
This code realizes the TF-IDF text representation, as a sub function, directly input parameters can be called to run, input parameter data two: text content and feature words. The corresponding weight of each feature word can be obtained by output.