toJson method Null safety

Implementation

Map<String, dynamic> toJson() {
  final Map<String, dynamic> data = <String, dynamic>{};
  data['2xs'] = _i2xs;
  data['xs'] = _xs;
  data['sm'] = _sm;
  data['md'] = _md;
  data['lg'] = _lg;
  data['xl'] = _xl;
  data['2xl'] = _i2xl;
  data['3xl'] = _i3xl;
  data['4xl'] = _i4xl;
  data['5xl'] = _i5xl;
  data['6xl'] = _i6xl;
  data['7xl'] = _i7xl;
  data['8xl'] = _i8xl;
  data['9xl'] = _i9xl;
  return data;
}