How I detect a colision with a Wall Sprite?

I'm using, emptyIDs) for generate the walls on the map.
I want to detect in collisionResponse(other), the collision of the objects specifically with the wall.

for example, if I want to detect a collision with the player I do:

function Object:collisionResponse(other)
    if other:isa(Player) then
        return 'overlap'

How I detect if other is a wall sprite?