code: @Override
  	public void encodeEnd(FacesContext context, UIComponent component) throws IOException {
  		if (!component.isRendered()) {
  			return;
  		}
  		ButtonGroup buttonGroup = (ButtonGroup) component;
  		ResponseWriter rw = context.getResponseWriter();
  		endDisabledFieldset(buttonGroup, rw);
  		rw.endElement("div");
  		String responsive = Responsive.getResponsiveStyleClass(buttonGroup, false).trim();
  		if(responsive.length() > 0) {
  			rw.endElement("div");
  		}
  		Tooltip.activateTooltips(context, buttonGroup);
  	}
docs: This methods generates the HTML code of the current b:buttonGroup.
  <code>encodeBegin</code> generates the start of the component. After the,
  the JSF framework calls <code>encodeChildren()</code> to generate the
  HTML code between the beginning and the end of the component. For
  instance, in the case of a panel component the content of the panel is
  generated by <code>encodeChildren()</code>. After that,
  <code>encodeEnd()</code> is called to generate the rest of the HTML code.
  
  @param context
  the FacesContext.
  @param component
  the current b:buttonGroup.
  @throws IOException
  thrown if something goes wrong when writing the HTML code.