Update main.py

main.py

@@ -4,7 +4,6 @@ from fastapi.middleware.cors import CORSMiddleware
 from fastapi import FastAPI, Request,  Header, BackgroundTasks, HTTPException, status
 import google.generativeai as genai_gen
 
-from collections import defaultdict
 from linebot import LineBotApi, WebhookHandler
 from linebot.exceptions import InvalidSignatureError
 from linebot.models import MessageEvent, TextMessage, TextSendMessage, ImageSendMessage, AudioMessage, ImageMessage