anchor.diff:  ///
   /// Durations are context independent. For example, a duration of 2 days is
   /// always 48 hours, even when it is added to a `DateTime` just when the
  -/// time zone is about to do a daylight-savings switch. (See [DateTime.add]).
  +/// time zone is about to make a daylight-savings switch. (See [DateTime.add]).
   ///
   /// Despite the same name, a `Duration` object does not implement "Durations"
   /// as specified by ISO 8601. In particular, a duration object does not keep
  
positive.code:   /// and it might lose precision.
    ///
    /// All arguments are 0 by default.
    const Duration(
        {int days = 0,
        int hours = 0,
  
negative.code:   /// Returns a string with hours, minutes, seconds, and microseconds, in the
    /// following format: `H:MM:SS.mmmmmm`. For example,
    /// ```dart
    /// var d = const Duration(days: 1, hours: 1, minutes: 33, microseconds: 500);
    /// print(d.toString()); // 25:33:00.000500
    ///
    /// d = const Duration(hours: 1, minutes: 10, microseconds: 500);
    /// print(d.toString()); // 1:10:00.000500
    /// ```
    String toString() {
      var microseconds = inMicroseconds;
  