This package is no longer functional.
It has been without a maintainer for a significant period of time, and is in need of sufficient work that any future coordinated efforts to build a framework for general extrapolation techniques would be better to start from scratch.
If you wish to do full sun potential field extrapolations, you should look at pfsspy.
solarbextrapolation was a library for extrapolating 3D magnetic fields from line-of-sight magnetograms.