Error fixes import

app.py

@@ -3,7 +3,7 @@ import requests
 from pdfminer.high_level import extract_text
 from langchain_community.vectorstores import Chroma
 from langchain_huggingface import HuggingFaceEmbeddings, ChatHuggingFace
-from langchain_core.runnables import RunnablePassthrough
+from langchain_core.runnables import RunnablePassthrough, Runnable
 from io import BytesIO
 from langchain_core.output_parsers import StrOutputParser
 from langchain_core.documents import Document