如何修改代码，可以使得sentences只包含keyword所在的句子（keyword只匹配一次）？

import re

with open(f'keyword.txt', 'r') as file:
   keyword = [word.strip() for word in file.readlines()]
with open(f'file.txt', 'r') as file:
   article = file.read()

unmatched_keywords = []
for word in keyword:
   pattern = re.compile(fr'\b{re.escape(word)}\b')
   match = re.search(pattern, article)
   if match:
       article = re.sub(pattern, f"<b>{match.group()}<b>", article, count=1)
   else:
       unmatched_keywords.append(word)
      
with open(f"new.txt", "w") as file:
   file.write(article)
  
with open(f'unmatched_keywords.txt', 'w') as file:
   for word in unmatched_keywords:
       file.write(word + '\n')
      
# 使用正则表达式查找所有含有关键词的句子
pattern = r'[^.]*' + str(keyword) + r'[^.]*'
sentences = re.findall(pattern,article)

# 打印结果
with open(f"sentences.txt", "w") as file:
   #file.write(sentences)
   file.write('\n'.join(sentences))

一段代码，要求keyword匹配file，同时生成三个文件，一个文件是修改以后的file，一个是未匹配的关键字unmatchd，还有一个是关键字所在的句子sentences，但是按照上述代码的运行结果，sentences文件是整篇文章；
如何修改代码，可以使得sentences只包含keyword所在的句子（keyword只匹配一次）？

那你先按句子进行分割，然后循环去匹配关键字，不要整篇文章去匹配