Update utils.py

utils.py

@@ -18,6 +18,7 @@ from   langchain.evaluation        import StringEvaluator
 from   typing                      import Any, Optional
 from   langsmith.client            import Client
 from   langchain.smith             import RunEvalConfig, run_on_dataset
+from   langchain.chains.combine_documents.stuff import StuffDocumentsChain
 import streamlit as st
 import together
 import textwrap