code: public void setNoneSelectedText(final String noneSelectedText) {
          if (noneSelectedText != null)
              attrMixin.setAttribute(NONE_SELECTED_TEXT, noneSelectedText);
          else
              attrMixin.removeAttribute(NONE_SELECTED_TEXT);
      }
docs: Sets the text that is displayed when a multiple select
  has no selected options.<br>
  <br>
  Defaults to <code>Nothing Selected</code>.
  
  @param noneSelectedText