Update mc4-sampling.py

mc4-sampling.py

@@ -277,6 +277,7 @@ class Mc4SamplingConfig(datasets.BuilderConfig):
             languages (:obj:`List[str]`): list of languages to load
             **kwargs: keyword arguments forwarded to super.
         """
+        assert name is not None or languages is not None
         super().__init__(
             *args,
             name=name or "+".join(languages),