Correct method to fetch thumbnail image for VideoNote entity.

src/Entities/VideoNote.php

@@ -15,13 +15,21 @@ namespace Longman\TelegramBot\Entities;
  *
  * @link https://core.telegram.org/bots/api#videonote
  *
- * @method string getFileId()   Unique identifier for this file
- * @method int    getLength()   Video width and height as defined by sender
- * @method int    getDuration() Duration of the audio in seconds as defined by sender
- * @method PhotoSize getThumb() Optional. Video thumbnail as defined by sender
- * @method int    getFileSize() Optional. File size
+ * @method string    getFileId()   Unique identifier for this file
+ * @method int       getLength()   Video width and height as defined by sender
+ * @method int       getDuration() Duration of the audio in seconds as defined by sender
+ * @method PhotoSize getThumb()    Optional. Video thumbnail as defined by sender
+ * @method int       getFileSize() Optional. File size
  */
 class VideoNote extends Entity
 {
-
+    /**
+     * {@inheritdoc}
+     */
+    protected function subEntities()
+    {
+        return [
+            'thumb' => PhotoSize::class,
+        ];
+    }
 }