Both features use `groupby(discovery_service.plugins(), key=lambda p: p.type)`, which (per [the docs](https://docs.python.org/3.6/library/itertools.html#itertools.groupby)), requires the input iterable to already be sorted on the same key function, which is not the case for `discovery_service.plugins()`, which lists all custom plugins ahead of discovered plugins, resulting in the a mix of types.