Create a file 'success' when training is successful. This file doesn't need to have any content.
    See: https://docs.aws.amazon.com/sagemaker/latest/dg/your-algorithms-training-algo.html

def write_success_file():  # type: () -> None
    """Create a file 'success' when training is successful. This file doesn't need to have any content.
    See: https://docs.aws.amazon.com/sagemaker/latest/dg/your-algorithms-training-algo.html
    """
    file_path = os.path.join(_env.output_dir, 'success')
    empty_content = ''
    write_file(file_path, empty_content)