Thanks for looking at this

I believe this is effectively a port of findEdgePixels() to new-footprints. Is that correct Nate Lust? [For future reference, it's helpful to specify things like that in the ticket description.]

Sort of, as it is a different class, and works completely differently. In practice it is supposed to have the same end result, so in that sense yes it is.

Everything looks good. I have no comments, other than appreciating that you also added very useful __repr__ and __str__ methods to SpanSets.

Before merging, please fix the typos in the commit message for b3b9fa8 ("bindsing", "debuggin").

Also, commit messages which say things like "additionally, ..." or "in addition, ..." are a red flag that you should be using more fine-grained commits. Please fix bugs and add new features on separate commits.

Also also, I think some more documentation would be helpful. What does it mean to "find the pixels that are on the border of the SpanSet"? Does that mean they are inside the SpanSet but touching its edge? Or outside the SpanSet but adjacent to it? Or both?

merged to pybind11 branch