code: protected void addExtraOptions(ArgOptions options) {
      super.addExtraOptions(options);
  
      options.addOption('p', "permutationFunction",
                        "Specifies the permutation function to apply on " +
                        "index vectors. (Default: none)",
                        true, "CLASSNAME", "Optional");
  
      options.addOption('l', "indexVectorLength",
                        "Specifies the length of index vectors.",
                        true, "CLASSNAME", "Required");
    }
docs: {@inheritDoc}.