backend_draws_array     Posterior draws of a fit as an iterations x
                        chains x parameters array
backend_extract         Extract named parameters from a fit as a list
                        of arrays
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
use_flexstanr           Wire flexstanr into a host package
