title: flutter dart JsonSerializable with inherited class
body: <p>I have the following two classes where one is extending from the other like this :</p>
  <pre><code>@JsonSerializable(nullable: true)
  class Response {
    final String responseCode;
    final String responseMessage;
    final String errorLog;
    Response({this.errorLog, this.responseCode, this.responseMessage});
    factory Response.fromJson(Map&lt;String, dynamic&gt; json) =&gt;
        _$ResponseFromJson(json);
  }
  </code></pre>
  <p>.........................................................</p>
  <pre><code> @JsonSerializable(nullable: false)
  class Verify extends Response {
    Data data;
    Verify({
      this.data,
    });
    factory Verify.fromJson(Map&lt;String, dynamic&gt; json) =&gt; _$VerifyFromJson(json);
    Map&lt;String, dynamic&gt; toJson() =&gt; _$VerifyToJson(this);
  }
  </code></pre>
  <p>and whenever I'm trying to read <strong>response</strong> class properties from Verify  class, it's always null.</p>
  <p>so please how to achieve this?</p>