Update app.py

app.py

@@ -4,7 +4,8 @@ from PyPDF2 import PdfReader
 from langchain.text_splitter import CharacterTextSplitter
 from langchain.embeddings import OpenAIEmbeddings, HuggingFaceInstructEmbeddings
 from langchain.vectorstores import FAISS
-from langchain.chat_models import ChatOpenAI
+from langchain.chat_models import Chat
+
 from langchain.memory import ConversationBufferMemory
 from langchain.chains import ConversationalRetrievalChain
 from htmlTemplates import css, bot_template, user_template, hide_st_style, footer