Update app.py

app.py

@@ -18,7 +18,7 @@ from langchain_community.tools.arxiv.tool import ArxivQueryRun
 from langgraph.graph import StateGraph, START, END
 from langgraph.prebuilt import ToolNode
 from langgraph.prebuilt import tools_condition
-from langgraph.prebuilt import ToolInvocation
+from langgraph.schema import ToolInvocation
 from langgraph.prebuilt.tool_executor import ToolExecutor
 from dataclasses import dataclass
 from typing import TypedDict, List, Annotated, Literal