simpleQuery method
Implementation
Future<String> simpleQuery({
  String? model,
  List<Message> history = const [],
  Duration? delay,
  required String prompt,
  String? system,
  String role = 'user',
  List<Context>? contexts,
}) async {
  final result = await query(
    model: model,
    delay: delay,
    history: history,
    system: system,
    contexts: contexts,
    message: Message(type: MessageType.values.byName(role), content: prompt),
  );
  return result.message!;
}