private VisualElement CreateSampleItemInt(SampleItemInt item)
            {
                var field = new IntegerField(nameof(SampleItemInt.IntValue));

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

            foldout.text = key;

            var field = new IntegerField(nameof(SampleItemInt.IntValue));

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

            return(foldout);
        }