/// <summary>
 /// Method unregisters this observer from event.
 /// </summary>
 /// <param name="weather">
 /// The manager of events.
 /// </param>
 public void Unregister(WeatherManager weather) => weather.Weather -= WeatherMessage;
 /// <summary see cref="StatisticReport">
 /// Constructor registers this observer on event.
 /// </summary>
 /// <param name="weather">
 /// The manager of events.
 /// </param>
 public CurrentConditionsReport(WeatherManager weather)
 {
     weather.Weather += WeatherMessage;
 }