Update app.py

app.py

@@ -6,7 +6,7 @@ from PyPDF2 import PdfReader
 from langchain.text_splitter import RecursiveCharacterTextSplitter
 from langchain_community.embeddings.huggingface import HuggingFaceEmbeddings
 from langchain.vectorstores import chroma
-#from langchain.chains.retrieval_qa.base import RetrievalQA
+from langchain.chains.retrieval_qa.base import RetrievalQA
 from langchain.chains.question_answering import load_qa_chain
 from langchain_community.llms import huggingface_hub
 from langchain.document_loaders.pdf import PyMuPDFLoader