    def get_checkpoint_state(self) -> Optional[TrainerCheckpoint]:
        """
        Returns a tuple of (model state, training state), where training state could have several
        internal components (e.g., for an, optimizer, learning rate scheduler, etc.).
        """
        raise NotImplementedError
Returns a tuple of (model state, training state), where training state could have several
internal components (e.g., for an, optimizer, learning rate scheduler, etc.).
allennlp/training/trainer.py