def pointSize(self, s=None):
        """Set/get actor's point size of vertices."""
        if s is not None:
            if isinstance(self, vtk.vtkAssembly):
                cl = vtk.vtkPropCollection()
                self.GetActors(cl)
                cl.InitTraversal()
                a = vtk.vtkActor.SafeDownCast(cl.GetNextProp())
                a.GetProperty().SetRepresentationToPoints()
                a.GetProperty().SetPointSize(s)
            else:
                self.GetProperty().SetRepresentationToPoints()
                self.GetProperty().SetPointSize(s)
        else:
            return self.GetProperty().GetPointSize()
        return self
Set/get actor's point size of vertices.