Update app.py

app.py

@@ -8,7 +8,7 @@ from huggingface_hub import InferenceClient
 from langchain_text_splitters import RecursiveCharacterTextSplitter
 from langchain_community.vectorstores import Chroma
 from langchain_community.document_loaders import PyPDFLoader
-from langchain.chains import RetrievalQA
+from langchain_classic.chains import RetrievalQA
 from langchain_community.embeddings import HuggingFaceEmbeddings