Code Changes - Updated the imports

ragbench.py

@@ -1,13 +1,15 @@
 import os
 import pickle
-from typing import List, Dict, Any
+from typing import List
 import re, json
 from dataclasses import dataclass
 from nltk.tokenize import sent_tokenize
 from langchain_community.embeddings import HuggingFaceEmbeddings
 from huggingface_hub import InferenceClient
 from langchain_community.vectorstores import FAISS
-from langchain_community.retrievers import BM25Retriever, EnsembleRetriever
+from langchain_community.retrievers import BM25Retriever
+from langchain.retrievers import EnsembleRetriever  # Main LangChain package
+
 from langchain.schema import Document as LangchainDocument
 
 import torch