How to parse Orphanet OWL file (new version 4.0) part_of relationship

[LM-Ontologies]

I would like some advice on parsing Orphanet OWL file (new model) where part_of relationship is now represented differently.

In the previous version 3.3, part_of relationship is represented with the tag "BFO_000050".
However, in the new version 4.0, it is now represented with "Orphanet_C021".

pronto's relationship attributes can't seem to be able to pick up the part_of relationships.
Any advice on how to pick up those as relationships?

Thanks!