MRG and its corresponding codes

[tangyipeng100]

For Pointnet++, the paper has mentioned both MRG and MSG methods in 3.2 Hierarchical Point Set Feature Learning. In ./models/pointnet2_util.py, there are PointNetSetAbstractionMsg class and PointNetSetAbstraction class. I think PointNetSetAbstractionMsg class refers to the MSG method. Does PointNetSetAbstraction class(pointnet2_sem_seg.py) refers to the MRG method? I have not seen the concatenation steps in the codes.