Update retriever.py

retriever.py

@@ -7,8 +7,8 @@ from langchain_community.embeddings import SentenceTransformerEmbeddings
 
 import os
 from dotenv import load_dotenv
-from langchain_community.retrievers import BM25Retriever, EnsembleRetriever
-# from langchain.retrievers import BM25Retriever, EnsembleRetriever
+from langchain_community.retrievers import BM25Retriever
+from langchain.retrievers import EnsembleRetriever
 from kiwipiepy import Kiwi
 load_dotenv()