toJson method
Implementation
Map<String, dynamic> toJson() {
final _json = <String, dynamic>{};
if (isbn != null) {
_json[r'isbn'] = isbn;
}
if (releaseDate != null) {
_json[r'release_date'] = releaseDate;
}
_json[r'tags'] = tags;
_json[r'authors'] = authors;
return _json;
}