docs: public void makeInvisible() {
      CSSClass cls = new CSSClass(this, "unused");
      cls.setStatement(SVGConstants.CSS_FILL_OPACITY_PROPERTY, "0");
      cls.setStatement(SVGConstants.CSS_CURSOR_PROPERTY, SVGConstants.CSS_POINTER_VALUE);
      SVGUtil.setAtt(element, SVGConstants.SVG_STYLE_ATTRIBUTE, cls.inlineCSS());
    }