toMap method
Implementation
Map<String, dynamic> toMap() => <String, dynamic>{
'maximum': maximum == null
? null
: "${maximum!.year.toString().padLeft(4, '0')}-${maximum!.month.toString().padLeft(2, '0')}-${maximum!.day.toString().padLeft(2, '0')}",
'minimum': minimum == null
? null
: "${minimum!.year.toString().padLeft(4, '0')}-${minimum!.month.toString().padLeft(2, '0')}-${minimum!.day.toString().padLeft(2, '0')}",
};