docs: @Nonnull
    public static <IMPLTYPE extends IHCElementWithChildren <?>> IMPLTYPE makeDropdownToggle (@Nonnull final IMPLTYPE aElement)
    {
      aElement.addClass (CBootstrapCSS.DROPDOWN_TOGGLE).addChild (new BootstrapCaret ());
      aElement.customAttrs ().setDataAttr ("toggle", "dropdown");
      aElement.customAttrs ().setAriaHasPopup (true);
      aElement.customAttrs ().setAriaExpanded (false);
      return aElement;
    }