code: @CommandArgument
    public void addroles(
        @OptionArgument("username") String username,
        @OptionArgument("roles") String roles) {
  
      User user = users.get(username);
  
      if (user != null) {
        user.roles.addAll(Arrays.asList(roles.split(",")));
      } else {
        System.err.println(String.format("User '%s' does not exist", username));
      }
  
    }
docs: Add roles for a user.
  @param username The username of the user for whom to add roles.
  @param roles A comma-separated list of the roles to add.