If the object argument is a <stanfit> object, it simply returns the
result of rstan::extract(). If it is a <CmdStanMCMC> it returns samples
in the same format as rstan::extract() does for <stanfit> objects.
extract_samples(stan_fit, pars = NULL, include = TRUE)List of data.tables with samples
A <stanfit> or <CmdStanMCMC> object as returned by
fit_model().
Any selection of parameters to extract
whether the parameters specified in pars should be included
(TRUE, the default) or excluded (FALSE)