title: Is it possible to enforce parameter to be a key of certain type?
body: <p>Say we have the following lodash usage:</p>
  
  <pre><code>type Baz = {
      sortOrder: number
  }
  
  const baz: Baz;
  
  _.chain(baz)
      .sortBy("sortOrder")
      .value();
  </code></pre>
  
  <p>Would it be possible to restrict <code>"sortOrder"</code> to be <code>keyof Baz</code> without overriding <code>.sortBy</code> type definitions, or have to extract <code>"sortOrder"</code> to a variable?</p>