backend_draws_array     Posterior draws of a fit as an iterations x
                        chains x parameters array
backend_extract         Extract parameters from a fit, in a chosen
                        format
backend_generate_quantities
                        Run generated quantities against a fit and
                        return a parameter matrix
backend_has_draws       Does a fit object carry usable posterior draws?
fit_model               Fit a Stan model through the chosen backend
stan_options            Stan Sampler Options
test_threaded           Does a set of sampler options ask for
                        within-chain threading?
use_flexstanr           Wire flexstanr into a host package
