Update app.py

app.py

@@ -8,7 +8,7 @@ from langchain_community.vectorstores import Chroma
 from langchain_core.messages import HumanMessage, AIMessage, ToolMessage
 from langchain.text_splitter import RecursiveCharacterTextSplitter
 from langgraph.graph import END, StateGraph  # Removed START import
-from langgraph.nodes import ToolNode
+from langgraph.nodes.tool_node import ToolNode
 from langgraph.graph.message import add_messages
 from typing_extensions import TypedDict, Annotated
 from typing import Sequence