Sanity check the type of id2label and label2id arguments of from_pretrained...

Sanity check the type of id2label and label2id arguments of from_pretrained for TokenClassification models (#21490)

* Sanity check the type of id2label and label2id arguments of from_pretrained for TokenClassification models

* Incorporate PR feedbacks

* Incorporate PR feedbacks

src/transformers/configuration_utils.py

@@ -313,7 +313,11 @@ class PretrainedConfig(PushToHubMixin):
         self.finetuning_task = kwargs.pop("finetuning_task", None)
         self.id2label = kwargs.pop("id2label", None)
         self.label2id = kwargs.pop("label2id", None)
+        if self.label2id is not None and not isinstance(self.label2id, dict):
+            raise ValueError("Argument label2id should be a dictionary.")
         if self.id2label is not None:
+            if not isinstance(self.id2label, dict):
+                raise ValueError("Argument id2label should be a dictionary.")
             num_labels = kwargs.pop("num_labels", None)
             if num_labels is not None and len(self.id2label) != num_labels:
                 logger.warning(