title: Parse JSON to Map in flutter
body: <p>I get response from backend:</p>
  
  <pre><code>   {"measurements": {
              "pm10": {
                "name": "pm10",
                "value": 20.8647,
                "unit": "µg/m³"
              },
               "pm25": {
                "name": "pm10",
                "value": 20.8647,
                "unit": "µg/m³"
              },
               "o2": {
                "name": "pm10",
                "value": 20.8647,
                "unit": "µg/m³"
              }
  
          },
     "station": {
          "city": "{cityName}",
          "name": "{locationName}",
          "latitude": "54.353336",
          "longitude": "18.635283"
      }
      }
  </code></pre>
  
  <p>This is what I got at this moment:</p>
  
  <pre><code>class Pollutions {
  
      Pollutions.fromJsonMap(Map&lt;String, dynamic&gt; map):
                  measurements = Measurements.fromJsonMap(map["measurements"]),
                  station = Station.fromJson(map["station"]);
  
    Map&lt;String, Pollution&gt; measurements;
    Station station;
  
      Map&lt;String, dynamic&gt; toJson() {
          final data = Map&lt;String, dynamic&gt;();
          data['measurements'] = measurements == null ? null : measurements.jsonDecode(measurements);
          data['station'] = station == null ? null : station.toJson();
          return data;
      }
  }
  </code></pre>
  
  <p>and in measurements I can get other values and I don't know anything about they names, it could be o2, o3, not only pm10 etc. Can I parse this measurements to map key-value, where key will be pm10, something like that: Map?
  How should looks <code>Pollutions.fromJsonMap</code> and <code>toJson</code> methods for map?</p>