missing RetrievalQA chain added

app.py

@@ -10,6 +10,7 @@ from langchain.embeddings.openai import OpenAIEmbeddings
 from langchain.vectorstores import Pinecone
 from langchain.chains import ConversationChain
 from langchain.retrievers.self_query.base import SelfQueryRetriever
+from langchain.chains import RetrievalQA
 from langchain.chains.query_constructor.base import AttributeInfo
 
 pinecone.init(