AIC and BIC penalise a maximised log-likelihood. logLik.tulpa_fit() reports
one only for a fit that maximised over every parameter it reports
(quantity = "log_likelihood", as agq_fit() does); a mean log posterior, a
log evidence and a conditional log marginal likelihood are not, and both
criteria refuse them rather than return a number. Compare those fits by
their evidence, or by compare_models(criterion = "waic") / "loo".
Value
As stats::AIC() / stats::BIC() for maximised log-likelihoods;
errors otherwise.