How can I make vtkExtractSelectedIds return a vtkPolyData?

vtkExtractSelectedIds can return extracting cells as polydata even when preserving topology is off (template method vtkExtractSelectedIdsCopyCells is called with vtkPolyData as template argument). However the base class RequestDataObject method enforces a vtkUnstructuredGrid as output data object. So I don’t see how I can get a vtkPolyData back from this filter, unless I’m overlooking something?

I would prefer receiving the same type of data object as the input data type, which is the general intent of this filter, and the fact that the filter explicitly implements the copying into a vtkPolyData suggests that this was the intended behavior. I think this can be achieved quite easily by overriding the RequestDataObject method in vtkExtractSelectedIds.