def METHOD_NAME(p):
    seed_group = p.add_argument_group(
        'Seeding options', 'When no option is provided, uses --npv 1.')
    seed_sub_exclusive = seed_group.add_mutually_exclusive_group()
    seed_sub_exclusive.add_argument('--npv', type=int,
                                    help='Number of seeds per voxel.')
    seed_sub_exclusive.add_argument('--nt', type=int,
                                    help='Total number of seeds to use.')