ergm_propagate_ext.encode() is a convenience
function to propagate the extended state encoder to submodels if
they have any.
ergm_no_ext.encode() checks if a submodel contains
terms that use extended states and stops with an informative
error message if any do.
ergm_propagate_ext.encode(submodel)ergm_no_ext.encode(submodel)
ergm_propagate_ext.encode returns a list with one
element, ext.encode containing a function that follows the
extended state encoder API and simply returns a list of the
subterms extended state encodings.
the ergm_model to which the encoders should be
propagated.