code: @SafeVarargs
      public final SubCommandSet addAll(SubCommand<SubCommandDef>... subCommands) {
          for (SubCommand<SubCommandDef> subCommand : subCommands) {
              add(subCommand);
          }
          return this;
      }
docs: Add a set of sub-commands to the sub-command-set.
  
  @param subCommands The sub-commands to add.
  @return The sub-command-set.