letDateTimeOrNull function
Implementation
DateTime? letDateTimeOrNull(dynamic input) {
  if (input is DateTime) return input;
  if (input is String) return DateTime.tryParse(input);
  return null;
}DateTime? letDateTimeOrNull(dynamic input) {
  if (input is DateTime) return input;
  if (input is String) return DateTime.tryParse(input);
  return null;
}