Update app.py

app.py

@@ -8,6 +8,7 @@ from langchain_openai import ChatOpenAI
 from langchain_core.tools import tool
 from langchain_core.utils.function_calling import convert_to_openai_tool
 from langgraph.graph import StateGraph, END
+from langchain_core.messages import BaseMessage
 
 
 # Environment Setup