toJson method Null safety

Implementation

@override
Map<String, dynamic> toJson() => {
      "temp": temp,
      "feels_like": feelsLike,
      "temp_min": tempMin,
      "temp_max": tempMax,
      "pressure": pressure,
      "humidity": humidity,
      "sea_level": seaLevel,
      "grnd_level": grndLevel,
    };