    selector = vtkThreshold()
    selector.SetInputArrayToProcess(0, 0, 0, vtkDataObject().FIELD_ASSOCIATION_CELLS,
                                    vtkDataSetAttributes().SCALARS)
    selector.SetInputConnection(pad.GetOutputPort())
    selector.SetLowerThreshold(start_label)
    selector.SetUpperThreshold(end_label)
--
    selector = vtkThreshold()
    scalars_off = vtkMaskFields()
    geometry = vtkGeometryFilter()
    writer = vtkXMLPolyDataWriter()

    # Define all of the variables
