class BaseModel:
    """
    All Model classes should extend BaseModel.
    """

    def load_model(self):
        """
        Defining the network structure and return
        """
        raise NotImplementedError(".load() must be overridden.")

    def train(self, dataset_dir, epoch, batch_size, ckpt_path, history_save_path,
              train_dir_name='train', validate_dir_name='test'):
        """
        Model training process
        """
        raise NotImplementedError(".train() must be overridden.")