Hi there,
It's come to my attention that while benchmarking against my own implementation of the Leiden community algorithm, which was merged into networkit a while ago, someone has found that it's able to produce disconnected communities. (https://arxiv.org/html/2312.13936v5)

As this is not possible by design of the Leiden algorithm itself this is likely an implementation bug.
Im unable to confirm this but I'm a little embarassed to say that I might actually have forgotten to test for disconnected communities ..

If noone has time or the knowledge to confirm/test this you might want to remove the algorithm from the library (or provide a warning)

Greets