Make `NerModel.__init__()` lazy and add `str()` and `repr()`

    NUM_VALIDATION_SAMPLES = CONFIG.getint('number_of_validation_samples')

    STOPPING_PATIENCE = CONFIG.getint('stopping_patience')

    def __init__(self, model: AutoModelForTokenClassification):

        self.model = model

    def __init__(self, model_name_or_basename: str):

        self.model_name_or_basename = model_name_or_basename

    @property

    def model(self) -> AutoModelForTokenClassification:

        model = AutoModelForTokenClassification.from_pretrained(self.model_name_or_basename)

    def __str__(self) -> str:

        return self.model_name_or_basename

    def __repr__(self) -> str:

        return '{}: {}'.format(self.__class__.__name__, self)

    @classmethod

    def train_and_save(cls, model_checkpoint_basename: str, model_basename: str,