How to tell if an optional argument that could be an Associative Array is missing

[#1]

As noted in the title, if I have a function that takes some argument that could be an Associative Array:

someFunc = Function( {arg1}, [...] )

And the argument is optional, how to I check `Is Missing`? When I try to use Is Missing in cases where the value does turn out to be an Associative Array I get the error "argument should be numeric in access or evaluation of 'Is Missing' , Is Missing/*###*/(aa)"

[#2 · Accepted solution]

err I was one search away... I just saw that Is Associative Array exists