public override void ClearUI()
        {
            if (m_Library == null)
            {
                return;
            }

            m_Library.RemoveFromHierarchy();
            m_Library = null;
        }
        public override void CreateUI()
        {
            var root = rootVisualElement;

            var viewportWindow = document.primaryViewportWindow;

            if (viewportWindow == null)
            {
                return;
            }

            var selection = viewportWindow.selection;
            var viewport  = viewportWindow.viewport;

            m_Library = new BuilderLibrary(this, viewport, selection, null, null);

            root.Add(m_Library);
        }