Fix "How to use" snippet

The current "How To Use Snippet" cannot be copy-pasted and executed because of two minor problems:

L31: Trailing comma on the import that causes an error in python.
`device` is undefined

README.md

@@ -28,9 +28,10 @@ import requests
 
 import torch
 from PIL import Image
-from transformers import AutoProcessor, AutoModelForZeroShotObjectDetection, 
+from transformers import AutoProcessor, AutoModelForZeroShotObjectDetection 
 
 model_id = "IDEA-Research/grounding-dino-base"
+device = "cuda:0"
 
 processor = AutoProcessor.from_pretrained(model_id)
 model = AutoModelForZeroShotObjectDetection.from_pretrained(model_id).to(device)