small suggestion for the code

Since I cannot add a line or two to the code (and do we want that edit anyway?), I leave a suggestion as issue below (while it is a small suggestion instead).

What I've done in my version, while running the PVdiags, is (after the line Tdict["P"] = dsin.pv.var('ens') edit the code and add an optional argument to the function calc_pvdiags() with e.g. the name compute_meanpv:

    if compute_meanpv:
         Tdict["pv_ensmean"] = dsin.pv.mean('ens')

The default value could then be set to False, as it was previously not a possible argument.