What happens if I set negative decays for HawkesExpKern

[HaochenWang1243]

Hi. When I pass in a decay matrix that contains negative entries to HawkesExpKern, no error is reported and fit() is also successful.
I'm wondering if the results (score, adjacency, baseline, etc.) I got in this case are sensible or corrupted?

[Mbompr]

That really looks frightening, I have no idea if this is valid or not but definitely I didn't have this in mind while implementing the lib. Use it at your own risks!