[Closed] simple boolean detect instances

I have a macro for our modelers that messes up (repeates accdientally) when an instance is in the selection set.

I found

areNodesInstances <node> <node> 

but if I have to compare each object in the selection to each object in the selection, that could slow things down. Also,I want the first instanced object (the “source” object) to be included

is there a simple Boolean test for if an object is an instance?
one that does not involve iteratively comparing it to other objects ?