def arg_parser():
    """
    Create an empty argparse.ArgumentParser.
    """
    import argparse
    return argparse.ArgumentParser(formatter_class=argparse.ArgumentDefaultsHelpFormatter)

def atari_arg_parser():
    """
    Create an argparse.ArgumentParser for run_atari.py.
    """
    parser = arg_parser()
    parser.add_argument('--env', help='environment ID', default='PongNoFrameskip-v4')
    parser.add_argument('--seed', help='RNG seed', type=int, default=0)
    return parser