    tetra = vtkTetra()
    for i in range(0, numberOfVertices):
        tetra.GetPointIds().SetId(i, i)

    cellArray = vtkCellArray()
    cellArray.InsertNextCell(tetra)
--
    parser.add_argument('cell_name', nargs='?', const='vtkTetra', default='vtkTetra', type=str, help='The cell name.')
    args = parser.parse_args()
    return args.cell_name


if __name__ == '__main__':
--
    tetra = vtkTetra()
    for i in range(0, number_of_vertices):
        tetra.GetPointIds().SetId(i, i)

    cell_array = vtkCellArray()
    cell_array.InsertNextCell(tetra)
--
    tetra = vtkTetra()

    tetra.GetPointIds().SetId(0, 0)
    tetra.GetPointIds().SetId(1, 1)
    tetra.GetPointIds().SetId(2, 2)
    tetra.GetPointIds().SetId(3, 3)
--
    tetra = vtkTetra()

    tetra.GetPointIds().SetId(0, 4)
    tetra.GetPointIds().SetId(1, 5)
    tetra.GetPointIds().SetId(2, 6)
    tetra.GetPointIds().SetId(3, 7)
