class ViewMode

class ViewMode extends ViewModeBase {
  
  /**
   * {@inheritdoc}
   */
  protected function initializeIterator() {
    $rows = [];
    $result = $this->prepareQuery()
      ->execute();
    while ($field_row = $result->fetchAssoc()) {
      $field_row['display_settings'] = unserialize($field_row['display_settings']);
      foreach ($this->getViewModes() as $view_mode) {
        // Append to the return value if the row has display settings for this
        // view mode and the view mode is neither hidden nor excluded.
        // @see \Drupal\field\Plugin\migrate\source\d6\FieldInstancePerViewMode::initializeIterator()
        if (isset($field_row['display_settings'][$view_mode]) && $field_row['display_settings'][$view_mode]['format'] != 'hidden' && empty($field_row['display_settings'][$view_mode]['exclude'])) {
          if (!isset($rows[$view_mode])) {
            $rows[$view_mode]['entity_type'] = 'node';
            $rows[$view_mode]['view_mode'] = $view_mode;
          }
        }
      }
    }
    return new \ArrayIterator($rows);
  }
  
  /**
   * {@inheritdoc}
   */
  public function query() {
    $query = $this->select('content_node_field_instance', 'cnfi')
      ->fields('cnfi', [
      'display_settings',
    ]);
    return $query;
  }
  
  /**
   * {@inheritdoc}
   */
  public function fields() {
    return [
      'display_settings' => $this->t('Serialize data with display settings.'),
    ];
  }
  
  /**
   * {@inheritdoc}
   */
  public function getIds() {
    $ids['view_mode']['type'] = 'string';
    return $ids;
  }
  
  /**
   * {@inheritdoc}
   */
  public function calculateDependencies() {
    $this->dependencies = parent::calculateDependencies();
    if (isset($this->configuration['constants']['targetEntityType'])) {
      @trigger_error('The constant targetEntityType is deprecated in drupal:9.2.0 and is removed in drupal:10.0.0. Use entity_type instead. See https://www.drupal.org/node/3208135', E_USER_DEPRECATED);
      $this->addDependency('module', $this->entityTypeManager
        ->getDefinition($this->configuration['constants']['targetEntityType'])
        ->getProvider());
    }
    return $this->dependencies;
  }

}