`fit.scan` modifies input parameter `fix_pars`

[0ctagon]

In fit.scan, this line fixes the parameter in the fit, but if the user provides his own fix_pars list, the parameter stays fixed once the scan if finished.

cabinetry/src/cabinetry/fit/__init__.py

Line 775 in e017f4d

fix_pars[par_index] = True # hold scan parameter constant in fits

I think adding a .copy() would fix the problem;

init_pars = init_pars.copy() or model.config.suggested_init()
fix_pars = fix_pars.copy() or model.config.suggested_fixed()

[alexander-held]

Thanks for catching this! That is definitely a bug. I think init_pars is fine since that is already copied in the loop but fix_pars needs the same treatment. It looks like ranking, where similar manipulation happens, is luckily already handling this correctly.