changed chunk generation

ref_seg_ger.py

@@ -74,7 +74,7 @@ _FEATURES = datasets.Features(
             names=list(chain.from_iterable([['B-' + x, 'I-' + x] for x in _LABELS])) + ['O']
         )),
         "labels_ref": datasets.Sequence(datasets.features.ClassLabel(
-            names=['B-ref', 'I-ref', 'O-ref']
+            names=['B-ref', 'I-ref', ]
         ))
         # These are the features of your dataset like images, labels ...
     }