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A general description is here.
The default ‘AIC’ and ‘BIC’ methods now check whether the ‘methods’ namespace is loaded rather than ‘stats4’. They still use ‘stats4::logLik’ (and ‘stats4::nobs’), but packages no longer need to load ‘stats4’ explicitly.
‘confint.default()’ now also works on S4 objects, as long as suitable ‘coef()’ and ‘vcov()’ methods exist.