private VisualElement CreateSampleItemString(SampleItemString item)
            {
                var field = new TextField(nameof(SampleItemString.StringValue));

                field.value = item.StringValue;
                field.RegisterValueChangedCallback(e => item.StringValue = e.newValue);
                return(field);
            }
        private VisualElement CreateSampleItemString(SampleItemString item, string key)
        {
            var foldout = new Foldout();

            foldout.text = key;

            var field = new TextField(nameof(SampleItemString.StringValue));

            field.value = item.StringValue;
            field.RegisterValueChangedCallback(e => item.StringValue = e.newValue);
            foldout.Add(field);

            return(foldout);
        }