Updating app.py

app.py

@@ -14,6 +14,7 @@ from langchain_core.messages import AnyMessage, HumanMessage, AIMessage, SystemM
 from typing import TypedDict, Annotated
 from langgraph.graph.message import add_messages
 from langchain_huggingface import HuggingFaceEndpoint, ChatHuggingFace
+from langchain.chat_models import ChatOpenAI
 
 # (Keep Constants as is)
 # --- Constants ---