ConfigEntityBundleBase - with API, how to get a list of configured fields

I have a entity (@ConfigEntityType) that extends ConfigEntityBundleBase

With api, how to get a list of configured fields in interface ?

I tried

$entity_field_definitions = \Drupal::service('entity_field.manager')->getFieldDefinitions('event_type', 'classic_form');

But I got this error

LogicException: Getting the base fields is not supported for entity type Event Type. in Drupal\Core\Entity\EntityFieldManager->buildBaseFieldDefinitions() (line 225 of core/lib/Drupal/Core/Entity/EntityFieldManager.php).