Update app.py

app.py

@@ -41,7 +41,7 @@ import streamlit_authenticator as stauth
 import database as db  # python文件同目录下的.py程序，直接导入。
 import deta
 from langchain.chat_models import ChatOpenAI
-from langchain import StorageContext, load_index_from_storage, GPTVectorStoreIndex, LLMPredictor, PromptHelper
+from llama_index import StorageContext, load_index_from_storage, GPTVectorStoreIndex, LLMPredictor, PromptHelper
 from llama_index import ServiceContext, QuestionAnswerPrompt
 import sys
 import time