simmons fitting

[zorrax2b]

Hi
thanks for the code

I tried to use the Simmons model fitting but it seems that the example
https://stoner-pythoncode.readthedocs.io/en/latest/classes/Stoner.analysis.fitting.models.tunnelling.simmons.html#Stoner.analysis.fitting.models.tunnelling.simmons
did not work

error related to plot function and fmt[ ]
I use anaconda & tested on jupyterlab and spyder