NegativeBinomial missing fit_regularized method #1454
see #1453 for an error this causes
the main problem is that the inherited start_params doesn't take the extra negbin parameters into account.
aside: finding the range of alpha to use for regularization is not obvious. needs to be relatively large in the larger (nobs=20,000) dataset alpha=10
I think by default we should not penalize the negbin parameter, e.g.
also: there are no documentation examples for fit_regularized