public function getButtonAnnotationOptions()
    {
        return [
            self::ANNOTATION_NONE     => _t(__CLASS__ . '.NONE', 'None'),
            self::ANNOTATION_BUBBLE   => _t(__CLASS__ . '.BUBBLE', 'Bubble'),
            self::ANNOTATION_INLINE   => _t(__CLASS__ . '.INLINE', 'Inline'),
            self::ANNOTATION_VERTICAL => _t(__CLASS__ . '.VERTICALBUBBLE', 'Vertical Bubble')
        ];
    }