Add asset Tags / vendorKeywords

Is it possible to add Tags / vendorKeywords to an asset via scripting?

I can assign an array to DzAsset::userKeywords and it shows up in the Content DB Editor, but when I assign an array to DzAsset::vendorKeywords, while I can read it back immedietly, it does not not show up in the Content DB Editor, nor if I look at the property via a new script execution.