I'd like to try out the saving derived fields feature that was discussed here http://lists.spacepope.org/pipermail/yt-users-spacepope.org/2013-February/00...
Unfortunately the merge (PR #416) is one of the ones whose comments are lost because of a deleted repository. Could someone here explain how to use this functionality, i.e. how to save a derived field to disk by writing out a GDF file? Or point me to the place in the docs where this is discussed?