Update app.py

app.py

@@ -1,6 +1,6 @@
 from fastapi import FastAPI, Request
 from fastapi.middleware.cors import CORSMiddleware
-from bertopic import BERTopic
+from bertopic._bertopic import BERTopic  # internal module that avoids plotting
 from sentence_transformers import SentenceTransformer
 import uvicorn