For selections of typeEGeometryTopologyType::Polygroup, the results are equivalent to first converting the selection to correspondingEGeometryTopologyType::Triangleselection and then finding the boundary vertices. This gives the intuitive result for face selections, but may or may not be what is desired for polygroup vertex/edge selections, because vertices/edges that seem to be on the interior of the polygroup selection may be considered border vertices if the tesselation is such that they are adjacent to unselected triangle vertices/edges.