Update functions.py

functions.py

@@ -30,6 +30,8 @@ from langchain.llms import OpenAI
 from langchain.callbacks.base import CallbackManager
 from langchain.callbacks.streaming_stdout import StreamingStdOutCallbackHandler
 from langchain.chains.chat_vector_db.prompts import CONDENSE_QUESTION_PROMPT
+from langchain import VectorDBQAWithSourcesChain
+
 
 from langchain.chat_models import ChatOpenAI
 from langchain.prompts.chat import (