Update app.py

app.py

@@ -1,7 +1,7 @@
 from langchain.docstore.document import Document
 from langchain.text_splitter import RecursiveCharacterTextSplitter
 from langchain_community.retrievers import BM25Retriever
-
+import re
 # Importing required libraries
 import warnings
 warnings.filterwarnings("ignore")