fix: error when saving multible labels for the same image

ui_refexp.py

@@ -233,10 +233,11 @@ class UIRefExp(datasets.GeneratorBasedBuilder):
             if image_id:
                 image_id = image_id.group(1)
                 if image_id in files_to_keep:
+                    image_bytes = file_obj.read()
                     for labels in image_labels[image_id]:
                         bb_json = json.dumps(labels["target_bounding_box"])
                         yield _id, {
-                            "image": {"path": file_path, "bytes": file_obj.read()},
+                            "image": {"path": file_path, "bytes": image_bytes},
                             "image_id": image_id,
                             "image_file_path": file_path,
                             "prompt": labels["prompt"],