[yt-dev] Non-periodic datasets and ghost zones

Hi all, What should we do (in general) about non-periodic datasets and getting ghost zones for the domain edges? This is the reason that the cookbook recipe simple_slice_with_multiple_fields.py fails -- it's trying to get vorticity (needs GZs) for a non-periodic dataset. Fixing the cookbook only requires swapping out the dataset, but I thought we should probably open this discussion up a bit too. -Matt