Update app.py

app.py

@@ -8,6 +8,7 @@ from langchain.prompts import ChatPromptTemplate, MessagesPlaceholder
 from langchain_core.runnables import RunnablePassthrough, RunnableLambda
 from langchain_core.messages import AIMessage, HumanMessage
 from langchain.chains import LLMChain, StuffDocumentsChain, MapReduceDocumentsChain, ReduceDocumentsChain
+from langchain.llms import HuggingFaceHub
 
 import yt_dlp
 import json