Update app.py

app.py

@@ -11,7 +11,8 @@ os.environ['OPENAI_API_KEY'] = os.environ['OPEN_API_KEY']
 st.title("Contracts Summary ")
 import pandas as pd
 
-from langchain.retrievers import BM25Retriever, EnsembleRetriever
+from langchain.retrievers import EnsembleRetriever
+from langchain_community.retrievers import BM25Retriever
 from langchain.schema import Document
 from langchain_community.vectorstores import Chroma
 from langchain_community.embeddings import HuggingFaceEmbeddings