Update utils.py

utils.py

@@ -4,9 +4,11 @@ from langchain.text_splitter import CharacterTextSplitter, RecursiveCharacterTex
 from langchain_community.vectorstores import Chroma
 from langchain_community.embeddings import HuggingFaceEmbeddings
 from langchain_community.retrievers import BM25Retriever
-from langchain.llms import OpenAI
+from langchain_community.llms import OpenAI
 from langchain_openai import ChatOpenAI
 from langchain.chains import RetrievalQA
+from langchain.schema import AIMessage, HumanMessage
+from langchain_core.prompts import ChatPromptTemplate, MessagesPlaceholder
 import os
 
 def split_with_source(text, source):