title: flutter problem in json parsing of dynamic key values
body: <p>Following is the output of my JSON</p>
  <pre><code>{
      &quot;success&quot;: true,
      &quot;data&quot;: {
          &quot;ones&quot;: [{
                  &quot;id&quot;: &quot;2&quot;,
                  &quot;username&quot;: &quot;LM10002&quot;
              },
              {
                  &quot;id&quot;: &quot;6&quot;,
                  &quot;username&quot;: &quot;LM10006&quot;
              }
          ],
          &quot;twos&quot;: [{
                  &quot;id&quot;: &quot;3&quot;,
                  &quot;username&quot;: &quot;LM10003&quot;
              },
              {
                  &quot;id&quot;: &quot;8&quot;,
                  &quot;username&quot;: &quot;LM10008&quot;
              }
          ],
          &quot;threes&quot;: [{
              &quot;id&quot;: &quot;4&quot;,
              &quot;username&quot;: &quot;LM10004&quot;
          }],
          &quot;fours&quot;: [{
                  &quot;id&quot;: &quot;5&quot;,
                  &quot;username&quot;: &quot;LM10005&quot;
              },
              {
                  &quot;id&quot;: &quot;14&quot;,
                  &quot;username&quot;: &quot;GT10014&quot;
              }
          ]
      }
  }
  </code></pre>
  <p>Here the keys <code>ones, twos, threes, fours</code> are dynamic key values
  I tried parsing and able to get the values of</p>
  <pre><code>  DownLineModel({this.success, this.data});
    DownLineModel.fromJson(Map&lt;String, dynamic&gt; json) {
      success = json['success'];
      data = json['data'];
      print(data);
  </code></pre>
  <p>how can i parse the json and find the key terms and again parse it.</p>