Update app.py

app.py

@@ -4,6 +4,18 @@ from typing_extensions import TypedDict
 
 from langgraph.graph import StateGraph, START, END
 from langgraph.graph.message import add_messages
+from langchain_anthropic import ChatAnthropic
+
+llm = ChatAnthropic(model="claude-3-5-sonnet-20240620")
+
+def chatbot(state: State):
+    return {"messages": [llm.invoke(state["messages"])]}
+
+
+# The first argument is the unique node name
+# The second argument is the function or object that will be called whenever
+# the node is used.
+graph_builder.add_node("chatbot", chatbot)
 
 
 class State(TypedDict):