you can get appearance assets via Python
appearanceAssets = FilteredElementCollector(doc).OfClass(AppearanceAssetElement).ToElements()
but this code cannot be used for thermal and structural (physical) assets, seems no ThermalAssetElement in Revit API
even though i’m only use appearance assets in my materials but unused thermal and structural (physical) assets are still existed in RVT so how to get rid of those via coding? i mean not via material
just found out that PropertySetElement will do the trick i.e.
other2Assets = FilteredElementCollector(doc).OfClass(PropertySetElement).ToElements()