fix bug

agent.py

@@ -64,8 +64,8 @@ graph = builder.compile()
 
 def get_answer(query):
   messages = [HumanMessage(content=query)]
-  messages = graph.invoke({"messages": messages})
-  return result["messages"][-1]["content"]
+  results = graph.invoke({"messages": messages})
+  return results["messages"][-1].content
 
 if __name__ == "__main__":
     question = "In the video https://www.youtube.com/watch?v=L1vXCYZAYYM, what is the highest number of bird species to be on camera simultaneously?"