Update app.py

app.py

@@ -27,7 +27,7 @@ def predict():
         img = Image.open(io.BytesIO(image_bytes))
 
         results = model(img, size=640)  # reduce size=320 for faster inference
-        return "{results.pandas().xyxy[0].to_json(orient="records")}"
+        return f"{results.pandas().xyxy[0].to_json(orient="records")}"
 
 
 if __name__ == "__main__":