ZED 5.1 Fusion retrieveMeasure

In 5.1 I’ve noticed an additional method param for fusion.retrieveMeasure. “reference_frame: the requested reference frame, by default BASELINK. it is only available for fused point clouds.” What exactly is this? How do I use it? FUSION_REFERENCE_FRAME doesn’t show up in docs. Can I now retrieve a fused point cloud from Fusion module?