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