* 'flatten' plugins. If the plugin only need to change a single value it
* can skip setting this attribute and let
* \Drupal\migrate\MigrateExecutable::processRow() handle the iteration.
* 'flatten' plugins. If the plugin only need to change a single value it
* can skip setting this attribute and let
* \Drupal\migrate\MigrateExecutable::processRow() handle the iteration.