l and  y_val is supplied.
        preprocess_mode (str):  Either &#39;standard&#39; (normal tokenization) or one of {&#39;bert&#39;, &#39;distilbert&#39;}
                                tokenization and preprocessing for use with
                                BERT/DistilBert text classification model.
        lang (str):            language.  Auto-detected if None.
        random_state(int):      If integer is supplied, train/test split is reproducible.
                                If None, train/test