toOptionsJSON method
Implementation
@override
void toOptionsJSON(StringBuffer buffer) {
  super.toOptionsJSON(buffer);
  if (playAsSoundButtonText != null) {
    buffer.writeAll(
        ['"playAsSoundButtonText":', jsonEncode(playAsSoundButtonText), ','],
        '');
  }
  if (playAsSoundClickAnnouncement != null) {
    buffer.writeAll([
      '"playAsSoundClickAnnouncement":',
      jsonEncode(playAsSoundClickAnnouncement),
      ','
    ], '');
  }
}