src/transformers/tokenization_utils_base.py/PreTrainedTokenizerBase/max_len_single_sentence
class PreTrainedTokenizerBase:    def max_len_single_sentence(self) -> int:
        """
        `int`: The maximum length of a sentence that can be fed to the model.
        """
        return self.model_max_length - self.num_special_tokens_to_add(pair=False)