docs: @Nonnull
    public static BootstrapButtonGroup createButtonAsDropDownMenuWithSeparateCaret (@Nonnull final BootstrapButton aButton,
                                                                                    @Nonnull final Consumer <? super BootstrapDropdownMenu> aMenuItemProvider)
    {
      final BootstrapButtonGroup aBG = new BootstrapButtonGroup ();
      aBG.addChild (aButton);
  
      final BootstrapButton aCaret = new BootstrapButton (aButton.getButtonType (), aButton.getButtonSize ());
      BootstrapDropdown.makeDropdownToggle (aCaret);
      aBG.addChild (aCaret);
  
      final BootstrapDropdownMenu aMenu = aBG.addDropDownMenu ();
      aMenuItemProvider.accept (aMenu);
      return aBG;
    }