extractRequiredList<T> function
Implementation
List<T> extractRequiredList<T>(Map<String, dynamic> json, String field,
Function(Map<String, dynamic>) parseCallback) {
if (json[field] == null) throw MissingRequiredFieldException(field);
if (!(json[field] is List)) throw FieldIsNotAListException(field);
return parseCallback(json[field]);
}