Expanded class hierarchy of RelationshipData in Drupal 8
- class \Drupal\jsonapi\JsonApiResource\Data implements \Drupal\jsonapi\JsonApiResource\IteratorAggregate, \Drupal\jsonapi\JsonApiResource\Countable
- class \Drupal\jsonapi\JsonApiResource\RelationshipData
- class \Drupal\jsonapi\JsonApiResource\ResourceObjectData implements TopLevelDataInterface