Update app.py

app.py

@@ -8,6 +8,7 @@ from IPython.display import Markdown, display
 from langchain.document_loaders import PyPDFLoader
 from langchain.embeddings import OpenAIEmbeddings
 from langchain.indexes import VectorstoreIndexCreator
+from langchain.text_splitter import CharacterTextSplitter
 from langchain.llms import OpenAI
 from langchain.vectorstores import DocArrayInMemorySearch
 from uuid import uuid4