A general likelihood model framework. When an object x implements
the concept of likelihood_model, it may be used to compute the
standard errors of the parameters of the model, maximum likelihood
estimates, the asymptotic sampling distribution of the MLE, and
other quantities.
is_likelihood_model(x)To satisfy the concept of likelihood_model, at a minimum the
object must implement ``loglik. For optimal results, it may also provide implementations for score`, and `hess_loglik` methods.