In Owlready2 how to merge the classes of one ontology with those of another?

Question

I am asking how to do something similar to what is unsuccessfully attempted here:

https://github.com/pwin/owlready2/issues/22

Reading the Owlready documentation it seems like: onto.imported_ontologies.append(owlready_ontology)

would permit onto to access owlready_ontology to somehow manipulate it. How can this be done?