It would be useful to be able to save MCMCChains objects as - [Stan CSV format](https://mc-stan.org/docs/cmdstan-guide/stan_csv_apdx.html), - [ArviZ format ](https://arviz-devs.github.io/ArviZ.jl/dev/api/data/#InferenceObjects.to_netcdf) - and JSON. cc @nsiccha