optional arguments with `nargs` issues

[ktbarrett]

    group.add_argument(
        "--lib-name-path",
        help="Print the absolute path of interface library for given interface (VPI/VHPI/FLI) and simulator",
        nargs=2,
        metavar=("INTERFACE", "SIMULATOR"),
    )

generates the following documentation

Only the first of the two metavars is printed and the (default: None) clause is unnecessary.