def format_timedelta(timedelta_obj):
    """Helper function to format timedelta to a human-readable time string"""
    if timedelta_obj:
        timedelta_string = '%02d:%02d:%02d' % (
            int(timedelta_obj.total_seconds() // 3600),
            (timedelta_obj.seconds // 60) % 60,
            timedelta_obj.seconds % 60
        )

        return timedelta_string

    return None