Update app.py

app.py

@@ -1,12 +1,17 @@
 import streamlit as st
 from dotenv import load_dotenv
 from PyPDF2 import PdfReader
-from langchain.text_splitter import RecursiveCharacterTextSplitter
-from langchain_community.embeddings import HuggingFaceEmbeddings
-from langchain_community.vectorstores import FAISS
-from langchain.llms import HuggingFaceHub
+from langchain.text_splitter import CharacterTextSplitter, RecursiveCharacterTextSplitter
+from langchain_community.embeddings import OpenAIEmbeddings, HuggingFaceInstructEmbeddings
+from langchain_community.vectorstores import FAISS, Chroma
+from langchain_community.embeddings import HuggingFaceEmbeddings  # General embeddings from HuggingFace models.
+from langchain.chat_models import ChatOpenAI
+from langchain.memory import ConversationBufferMemory
+from langchain.chains import ConversationalRetrievalChain
+from htmlTemplates import css, bot_template, user_template
+from langchain.llms import HuggingFaceHub, LlamaCpp, CTransformers  # For loading transformer models.
 from langchain_community.document_loaders import PyPDFLoader, TextLoader, JSONLoader, CSVLoader
-import tempfile  # 임시 파일을 생성하기 위한 라이브러리입니다.
+import tempfile # 임시 파일을 생성하기 위한 라이브러리입니다.
 import os
 
 def get_pdf_text(pdf_docs):