code: private void addArgument(CliArgumentContainer argumentContainer) {
  
      this.arguments.add(argumentContainer);
      String modeId = argumentContainer.getArgument().mode();
      requireMode(modeId, argumentContainer);
    }
docs: This method {@link #getArguments(CliModeObject) registers} the given {@link CliArgumentContainer argument}.
  
  @param argumentContainer is the {@link CliArgumentContainer argument} to register.