Hello! I've modified the Cosmology class is cosmology.py to take a couple of parameters for working with the Linder 2002 parameterization of w(a) = w_0 + w_a (1 - a) in dynamical dark energy, but leaving the cosmological constant as the default choice. However, because the cosmology class is used internally in yt in several places (where it takes its parameters from the dataset object itself), I was thinking it would make the most sense to add these parameters to the dataset object itself so that they could be set when loading data (as they're not actually stored in the simulation output itself). These parameters are a value for w_0, a value for w_a, and a flag saying whether or not to use dynamical dark energy or the cosmological constant. I tried looking at the yt source code to find where the best place to do this would be, but I just thought I would ask, just to be safe and sure about it. So, my question is: what do I need to modify in order to add those three parameters to a generic dataset object (I'm using gadget, but it would be nice if they were independent of simulation code) so that they can then be passed to the cosmology class in yt? Thanks! -Jared