Returns the deviance of a fitted model object.
A fitted model object from splm(), spautor(), spglm(), or spgautor(),
where estmethod is "ml" or "reml".
Other arguments. Not used (needed for generic consistency).
The deviance.
For objects estimated using "ml" or "reml",
the deviance is twice the difference in log-likelihoods between the
saturated (perfect-fit) model and the fitted model.