Update app.py

app.py

@@ -1,11 +1,11 @@
-import os
+  import os
 import gradio as gr
 from langchain.document_loaders import PyPDFLoader
 from langchain.text_splitter import RecursiveCharacterTextSplitter
 from langchain.embeddings import OpenAIEmbeddings
 from langchain.vectorstores import FAISS
 from langchain.chains.base import Chain
-from langchain.llms import ChatOpenAI
+from langchain.chat_models import ChatOpenAI
 from langchain.chains import LLMChain, ConversationalRetrievalChain
 from langchain.memory import ConversationBufferMemory
 from langchain.prompts import PromptTemplate