S3 generic converting a fitted model to a draws_matrix object.

Needs to be implemented for all types of objects the backend can return from SBC_fit(). Default implementation just calls, posterior::as_draws_matrix(), so if the fit object already supports this, it will work out of the box.

SBC_fit_to_draws_matrix(fit)

# S3 method for default
SBC_fit_to_draws_matrix(fit)