Dart APIunself_modelMappingoptions options property Null safety @JsonExtra() Map<String, dynamic> options inherited Implementation @JsonExtra() Map<String, dynamic> get options => throw _privateConstructorUsedError; unself_model unself_model Mapping options property Mapping class Constructors Mapping fromJson Properties copyWith extra fields from hashCode options runtimeType to Methods noSuchMethod toJson toString Operators operator ==