Yawl to Petri Nets

Hello for all,
I create an YAWL model and upload to server, that's all ok.
But, I need to convert an yawl specification model (YAWL file) to Petri Net file (pnml).
In this conversion, I need to convert from start, joins, splits into Petri net for use this model to simulation in another system.
Please, if someone used this conversion and could share the knowledge to do this conversion. How do this?