small fix

NLVR2.py

@@ -111,7 +111,7 @@ class NLVR2Dataset(datasets.GeneratorBasedBuilder):
             left_img_identifier = f"{split_name}-{common_img_identifier[1]}-{common_img_identifier[2]}-img0.png"
             right_img_identifier = f"{split_name}-{common_img_identifier[1]}-{common_img_identifier[2]}-img1.png"
             if split_name == "train":
-                directory = ex["directory"]
+                directory = str(ex["directory"])
                 left_image_path = str(os.path.join(images_path, directory, left_img_identifier))
                 right_image_path = str(os.path.join(images_path, directory, right_img_identifier))
             else: