This UI list based template to show assets in panels was initially
introduced for the new pose library in Blender 3.0. It enabled showing
pose assets in a grid with big previews in the 3D View Sidebar. Since
then this UI element has been superseded by the asset shelf. The
template was planned for removal since then, see #110461.
Note that the asset shelf is only available in a few editors so far,
while the template was available in all editors. So it's possible that
some add-ons still rely on this template. However, I haven't found any
add-on using this template. I think it's been broken a few times and we
didn't get reports about it either. So removal seems fine.
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