Hash/identifier for userdata objects for hs.axuielement to allow usage as table keys?

[pitkling]

I'm relatively new to Lua and recently realized that for userdata objects like axuielementObject given something like

systemElement  = hs.axuielement.systemWideElement()
currentElement1 = systemElement:attributeValue("AXFocusedUIElement")
currentElement2 = systemElement:attributeValue("AXFocusedUIElement")

the comparison currentElment1 == currentElement2 would return true, while after

table[currentElement1] = true

the entry table[currentElement2] is still nil. After doing some reading I see why, but I wonder whether there is some way to still use such axuielementObject objects as table keys? Something like currentElement1.id() or currentElement1.hash() that would uniquely identify a given ui element and could be used as table keys.