title: How to check 'late' variable is initialized in Dart
body: <p>In kotlin we can check if the 'late' type variables are initialized like below</p>
  <pre><code>lateinit var file: File    
  if (this::file.isInitialized) { ... }
  </code></pre>
  <p>Is it possible to do something similar to this in Dart..?</p>