The fields() methods are modified to accept the argument 'grids'; it was the easiest (but perhaps not the best way) to access the grids (which was necessary for the SC fields method: https://github.com/nlooije/sailfish/blob/multicomp/sailfish/lb_multi.py#L400). I tried a couple of ways to retrieve the grids from the 'cls' arg directly but was unable to. Maybe you can give an indication how to do this?