public void TestExisitngId()
        {
            var obj = new SimpleObjectWithId()
            {
                StringValue = "Name!",
                Id          = Guid.NewGuid().ToString()
            };

            var doc = obj.ToMutableDocument();

            var newObject = (SimpleObjectWithId)doc.ToObject();
        }
        public void TestNewId()
        {
            var obj = new SimpleObjectWithId()
            {
                StringValue = "Name!",
                Id          = null
            };

            var doc = obj.ToMutableDocument();

            var newObject = (SimpleObjectWithId)doc.ToObject();
        }