Specific per-entity building.
array $build: The render array that is being created.
Drupal\Core\Entity\EntityInterface $entity: The entity to be prepared.
string $view_mode: The view mode that should be used to prepare the entity.
string $langcode: (optional) For which language the entity should be prepared, defaults to the current content language.
protected function alterBuild(array &$build, EntityInterface $entity, $view_mode, $langcode = NULL) {
}