How would you go about getting the namecall method

so in metatables there is a metamethod called __namecall whenever you namecall something. an
example of which is:

local foo = newproxy(true)
getmetatable(foo).__namecall = print

foo:namecall(1,2,3) --> userdata, 1, 2, 3

I am wondering if there is a way of retrieving the namecall method used (in this case it would be ‘namecall’)