Please add cycle index in pybamm.lithium_ion.DFN.variable_names()

[kimes0726]

There are cycle information in summary variables (in name of "Cycle number") but not available in pybamm.lithium_ion.DFN.variable_names() sure i can use separately but if cycle information is available in pybamm.lithium_ion.DFN.variable_names() it would be great!

Thanks.

[valentinsulzer]

Summary variables (such as cycle index) are fundamentally tied to a solution of a simulation with an experiment. Otherwise there is no concept of a "cycle" to associate summary variables with. We do need to improve the utilities associated with summary variable names, this should be done as part of #1726

[kimes0726]

Oh i didn't know that

Thank you so much