Update app.py

app.py

@@ -2,7 +2,9 @@ import gradio as gr
 from langchain.prompts import ChatPromptTemplate
 from langchain_huggingface import HuggingFaceEndpoint
 from langchain.schema import HumanMessage, SystemMessage
-from langchain.callbacks
+from langchain.callbacks.base import BaseCallbackHandler
+import os
+import time
 
 # Custom streaming callback for Gradio
 class GradioStreamingCallback(BaseCallbackHandler):