We can set definition to a custom block like this.
It will have nothing inside, but at least number of inputs will change.
We also can set definition like this.
So, the thing is about getting definition later.
If it try to get definition of second one, it looks fine.
If i try to get definition of first one, it looks like this.
Why does it happen? It would be better, if we could get definition of nothing with input names.