EntityTypeInterface

class \Drupal\Core\Config\Entity\ConfigEntityType extends \Drupal\Core\Config\Entity\ConfigEntityTypeInterface implements \Drupal\Core\Entity\EntityType
class \Drupal\Core\Entity\ContentEntityType extends \Drupal\Core\Entity\ContentEntityTypeInterface implements \Drupal\Core\Entity\EntityType
class \Drupal\Core\Entity\EntityType extends \Drupal\Core\Entity\EntityTypeInterface uses \Drupal\Core\DependencyInjection\DependencySerializationTrait, \Drupal\Core\StringTranslation\StringTranslationTrait implements \Drupal\Component\Plugin\Definition\PluginDefinition
class \Drupal\Tests\views\Kernel\Entity\TestEntityType implements \Drupal\Core\Entity\ContentEntityType

Buggy or inaccurate documentation? Please file an issue. Need support? Need help programming? Connect with the Drupal community.