Fix tab format

NIH-Chest-X-ray-dataset.py

@@ -106,11 +106,11 @@ class XChest(datasets.GeneratorBasedBuilder):
 		# Iterate trought image folder and check if they belong to
 		# the trainset or testset
 		for batch in data_files:
-		  for img in batch:
+		  for img in dl_manager.download_and_extract(batch):
 		    if img in train_val_list:
 		      train_files.append(img)
 		    else:
-	              test_files.append(img)
+                      test_files.append(img)
 
 		print(train_files)
 		print(test_files)