如何在文本文件中包含特定单词的行的前后插入一行？

def insert_line(filename, word, line_to_insert):
    with open(filename, 'r') as file:
        lines = file.readlines()

    with open(filename, 'w') as file:
        for line in lines:
            file.write(line)
            if word in line:
                file.write(line_to_insert + '\n')

filename = 'example.txt'  # 文本文件名
word = 'specific_word'  # 特定单词
line_to_insert = 'This is the line to insert.'  # 要插入的行内容

insert_line(filename, word, line_to_insert)