src/transformers/configuration_utils.py/PretrainedConfig/num_labels
class PretrainedConfig:    def num_labels(self, num_labels: int):
        if not hasattr(self, "id2label") or self.id2label is None or len(self.id2label) != num_labels:
            self.id2label = {i: f"LABEL_{i}" for i in range(num_labels)}
            self.label2id = dict(zip(self.id2label.values(), self.id2label.keys()))