request the arguments for running

def get_args():
    """
    request the arguments for running
    """
    ap = argparse.ArgumentParser(description="Create frames for a movie that can be compiled using ffmpeg")
    ap.add_argument("start", help="date string as start time")
    ap.add_argument("end", help="date string as end time")
    ap.add_argument("step", type=float, help="fraction of a day to step by")
    ap.add_argument("--config", help="path to a config file", default="config.json")
    return ap.parse_args()