Update app.py

app.py

@@ -7,6 +7,7 @@ import pandas as pd
 from typing import TypedDict, Annotated
 from langgraph.graph.message import add_messages
 from langchain_core.messages import AnyMessage, HumanMessage, AIMessage
+from langgraph.prebuilt import ToolNode
 from langgraph.graph import StateGraph, START, END
 from langchain_community.tools import DuckDuckGoSearchRun
 from langchain_huggingface import HuggingFaceEndpoint, ChatHuggingFace