The results are placed in the post slot of the
stepwise-selected model that is returned.
There are up to two additional components.
There is an "anova"
component corresponding to the steps taken in the search,
as well as a "keep" component if the keep= argument
was supplied in the call.
This function is a direct adaptation of
for vglm-class objects.
Since step is not generic,
the name step4() was adopted
and it is generic, as well as being S4 rather than S3.
It is the intent that this function should work as similar as
possible to step.