Feature request: <I/sigma>, <I>, <sigma> from gemmi.Intensities.calculate_merging_stats()

[MartinMalyMM]

The method calculate_merging_stats()of the gemmi.Intensities object nowadays provides these:
[ 'all_refl', 'cc_half', 'cc_star', 'r_meas', 'r_merge', 'r_pim', 'stats_refl', 'unique_refl']
It could be nice if it also provided <I/sigma>, and (even when the reflections in the gemmi.Intensities object are not merged yet...)

[keitaroyam]

I think we can do this. However, <I/sigma> isn't a merging statistic in the sense that it doesn't require unmerged data. You could calculate <I/sigma> on the python side for now, which should be relatively straightforward.