title: Extract own class properties / members types
body: <p>Having the following classes</p>
  
  <pre><code>class Model {
    status: string;
    save(): Promise&lt;void&gt;
  }
  </code></pre>
  
  <pre><code>class Car extends Model {
    brand!: string;
    dataValues!: { [key in keyof this]: Exclude&lt;this[key], Function | undefined&gt; };
  }
  </code></pre>
  
  <pre><code>car.dataValues.status // exists;
  </code></pre>
  
  <p>How can I type <code>dataValues!</code> to get only <code>keysof</code> the <code>Car</code> class? (ownPropertyNames)</p>
  
  <p>Thanks a lot.</p>