[Solved] usage of AtlasContains ? Check if game image exists in atlas

[Serpens]

How should one use "TheSim:AtlasContains" function? Or how in general check if an image name exists in an atlas?

I don't add images myself, I would like to use the ones from the game, so I eg do:

_G.TheSim:AtlasContains("images/customisation.xml", "berrybush")

in modworldgenmain and also tried in modmain within AddPrefabPostInit, it always returns "false", although:
This image exists in that atlas AND I can use that image without problem when using the modutil functiion "AddCustomizeItem".

So how do I check withing modmain if an atlas image exists? I also tried
local customisation_xml = GLOBAL.resolvefilepath("images/customisation.xml")
but this did not change anything...

edit:
I it needs ".tex", so this will work:

_G.TheSim:AtlasContains("images/customisation.xml", "berrybush.tex")

I did not try that, because AddCustomizeItem does not require the ".tex"...

Edited July 23, 2022 by Serpens
added solution