private void Init(string title)
        {
            this.StyleFont(FontStyle.Bold);
            this.StyleMinHeight(20);
            this.StyleBorderWidth(0, 0, 1, 0);
            Color borderColor = EditorGUIUtility.isProSkin
                ? new Color32(35, 35, 35, 255)
                : new Color32(153, 153, 153, 255);

            this.StyleBorderColor(borderColor);

            headerElement = new HorizontalLayout();
            headerElement.StyleHeight(21);
            headerElement.StyleMaxHeight(21);
            headerElement.StyleMinHeight(21);
            headerElement.StylePadding(4, 0, 0, 0);
            headerElement.StyleAlignItem(Align.Center);
            Color backgroundColor = EditorGUIUtility.isProSkin
                ? new Color32(80, 80, 80, 255)
                : new Color32(222, 222, 222, 255);

            headerElement.StyleBackgroundColor(backgroundColor);
            Color hoverBorderColor = new Color32(58, 121, 187, 255);

            headerElement.RegisterCallback <MouseEnterEvent>((evt) =>
            {
                headerElement.StyleBorderWidth(1);
                headerElement.StyleBorderColor(hoverBorderColor);
            });
            headerElement.RegisterCallback <MouseLeaveEvent>((evt) =>
            {
                headerElement.StyleBorderWidth(0);
                headerElement.StyleBorderColor(Color.clear);
            });
            base.Add(headerElement);

            contentElement = new VerticalLayout();
            contentElement.StyleDisplay(value);
            base.Add(contentElement);

            labelElement      = new Label();
            labelElement.text = title;
            headerElement.Add(labelElement);

            imageElement      = new Image();
            imageElement.name = nameof(imageElement);
            imageElement.StyleMargin(0, 4, 0, 0);
            imageElement.StyleSize(16, 16);
            headerElement.Add(imageElement);
            imageElement.SendToBack();
            imageElement.RegisterCallback <GeometryChangedEvent>((evt) =>
            {
                imageElement.StyleDisplay(imageElement.image == null ? DisplayStyle.None : DisplayStyle.Flex);
            });

            foloutImage = new Image();
            foloutImage.StyleWidth(13);
            foloutImage.StyleMargin(0, 2, 0, 0);
            foloutImage.scaleMode = ScaleMode.ScaleToFit;
            foloutImage.image     = value ? onIcon : offIcon;
            if (!EditorGUIUtility.isProSkin)
            {
                foloutImage.tintColor = Color.grey;
            }
            headerElement.Add(foloutImage);
            foloutImage.SendToBack();


            headerElement.RegisterCallback <MouseUpEvent>((evt) =>
            {
                if (evt.button == 0)
                {
                    Value = !Value;
                    evt.StopPropagation();
                }
            });
        }