Accessing children of a relationship

Is it possible to access the children of a relationship? For example, with the method `term.subclasses()` I can access all the inverse `is_a` relationships. Is there a way to access other relationships this way? E.g `regulates` in GO?

I am new to the use of ontologies, so I am not sure if that's the case, but [this example](https://pronto.readthedocs.io/en/stable/api/pronto.Term.html#pronto.Term.objects) from the documentation seems to be doing exactly that.

```python
go = pronto.Ontology.from_obo_library("go.obo")
go['GO:0048870']
list(go['GO:0048870'].objects(go.get_relationship('part_of')))
```

However, when I run it I get this:

```
NotImplementedWarning: `Term.objects` is not semantically correct, most of the logic rules have not been implemented. Consider using an actual reasoner instead.
list(go['GO:0048870'].objects(go.get_relationship('part_of')))
```
Any tips on this?