public void Roundtrip2()
        {
            TimeSpan now = DateTime.UtcNow.TimeOfDay;

            var conv = new TimeSpanConverter("G");

            string?tmp = conv.ConvertToString(now);

            Assert.IsNotNull(tmp);

            var now2 = (TimeSpan?)conv.Parse(tmp);

            Assert.AreEqual(now, now2);
        }