https://api.drupal.org/api/drupal/core%21modules%21field%21src%21Plugin%21migrate%21source%21d6%21FieldInstancePerViewMode.php/9
FieldInstancePerViewMode.php | Drupal API
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https://api.drupal.org/api/drupal/core%21modules%21field%21src%21Plugin%21migrate%21source%21d6%21FieldInstancePerViewMode.php/class/FieldInstancePerViewMode/11.x
class FieldInstancePerViewMode | Drupal API
classdrupalapi