Make the model snippet self contained

README.md

@@ -42,6 +42,7 @@ from PIL import Image
 
 # load ADE20k image
 ds = load_dataset("hf-internal-testing/fixtures_ade20k", split="test")
+image = Image.open(ds[0]['file'])
 
 feature_extractor = BeitFeatureExtractor.from_pretrained('microsoft/beit-base-finetuned-ade-640-640')
 model = BeitForSemanticSegmentation.from_pretrained('microsoft/beit-base-finetuned-ade-640-640')