private void OnTreeItemExpandCollapsing(object sender, TreeExpandingEventArgs <object> e)
 {
     if (e.Parent is LevelEditorResource resource && resource.HasChildren())
     {
         for (int i = 0; i < resource.Children.Count; i++)
         {
             e.Children.Add(resource.Children[i]);
         }
     }
 }
 private void OnItemExpanding(object sender, TreeExpandingEventArgs <ILevelEditorObject> e)
 {
     if (e.Parent.HasChildren())
     {
         for (int i = 0; i < e.Parent.Children.Count; i++)
         {
             e.Children.Add(e.Parent.Children[i]);
         }
     }
 }