Implementing custom PeakWidthModel

[Peter Metz]

Hi All,

There is an example of overriding the default PDF PeakWidthModel in the ADD2019 tutorials (https://github.com/diffpy/add2016-pdfgui/blob/master/DiffPy-CMI-tutorial/08-Fit-Naphthalene-PDF-improved.py).

I would like to extend this by overloading the JeongPeakWidth model to add another r-dependence. I'm struggling to come up with what attributes and signatures the required PeakWidthModel should have, however.

Thanks for any advice,
Peter