I tried replicating the script from another forum “Auto Join Walls and Columns” On the forum it seems like it does what I want to achieve and I did exactly what’t on the forum script but I still get a warning:
This has been discussed before, but basically you need to create a new list of unrwrapped elements.
unwrapped = 
for i in IN:
you can define a function that does it if you need to unwrap multiple inputs efficiently.
or you can unwrap the element in the main function as well as @Nick_Boyts mentioned.
Then in order to have a good functioning joining node, you need to check if the elements are already joined and exclude those to avoid an error.
Also in the way it is written right now the node will return nulls even when the elements are successfully joined.If you want it to return booleans you need to add an aditional boolean list.
I tried unwrapping the elements two ways and now I get Empty List @viktor_kuzev I added the switchJoin Order. Is that what you mean by adding a boolean list?
How come this script is not working for me and it worked on the “Auto Join Walls and Columns” Forum?
No, I meant that the way you append your results will give you a list of nulls even if the joining succeeds.
You get empty lists because the JoinGeometry method requires 3 parameters - document, 1st element, 2nd element.
You’re providing only doc, 1st element.
And I still believe you need to unwrap the individual elements.