Parse command line arguments

def parse_args():
    """Parse command line arguments"""
    parser = argparse.ArgumentParser()
    parser.add_argument("font_path", help="Path to ttf font file or directory containing ttf files")
    parser.add_argument("--loss", help="'ctc' or 'warpctc' loss [Default 'ctc']", default='ctc')
    parser.add_argument("--cpu",
                        help="Number of CPUs for training [Default 8]. Ignored if --gpu is specified.",
                        type=int, default=8)
    parser.add_argument("--gpu", help="Number of GPUs for training [Default 0]", type=int)
    parser.add_argument("--num_proc", help="Number CAPTCHA generating processes [Default 4]", type=int, default=4)
    parser.add_argument("--prefix", help="Checkpoint prefix [Default 'ocr']", default='ocr')
    return parser.parse_args()