    def find_latest_checkpoint(self) -> Optional[Tuple[str, str]]:
        """
        Return the location of the latest model and training state files.
        If there isn't a valid checkpoint then return None.
        """
        checkpoints = self._find_all_checkpoints()
        if len(checkpoints) <= 0:
            return None
        last_checkpoint = max(checkpoints)
        return self._model_state_path(*last_checkpoint), self._training_state_path(*last_checkpoint)
Return the location of the latest model and training state files.
If there isn't a valid checkpoint then return None.
allennlp/training/checkpointer.py