649 refactor parsing

Shall fix #649. 

The tests for the OntologyParser have not been translated, yet. See #942 for that.
I'm not happy with the naming of this method, because `this` could mean anything. However, I can't come up with a better name. `parse_hets_result` or `parse_hets_output` are some suggestions, but I'm not very happy with them either.