Drupal 8 - Get user from node

Drupal 8 - Get user from node

$user_entity = $node->uid->entity;
$variables['author_name'] = $user_entity->get('field_display_name')->view();
$user_picture = $user_entity->get('user_picture')->getValue();
if (_user_has_picture($user_picture)) {
  $target_id = $user_picture[0]['target_id'];
  $variables['author_picture_uri'] = _get_user_picture_uri($target_id);
}
$variables['author_bio'] = $user_entity->get('field_bio')->view();
$variables['author_twitter'] = $user_entity->get('field_twitter_username')->value;
$variables['author_url'] = $user_entity->urlInfo()->toString();