Update backend.py

backend.py

@@ -22,7 +22,7 @@ import os
 from langchain.llms import OpenAI  # Import the OpenAI class
 from langchain.chat_models import ChatOpenAI  # Import ChatOpenAI
 from langchain.memory import ConversationBufferMemory
-from langchain.agents import create_openai_tools_agent, AgentExecutor
+from langchain.agents import create_openai_tools_agent, AgentExecutor, Tool
 from langchain.prompts import (
     ChatPromptTemplate,
     MessagesPlaceholder,