Update app.py

app.py

@@ -1,4 +1,7 @@
 from langchain.embeddings.openai import OpenAIEmbeddings
+from langchain.vectorstores import Chroma
+from langchain.text_splitter import CharacterTextSplitter
+from langchain.chains.question_answering import load_qa_chain
 from langchain.agents import create_csv_agent
 from langchain.llms import OpenAI
 import os