Drupal 8 Module Development - Second Edition

Bundles

The Node entity type happens to have bundles which is the reason why we have a bundle_label property as well:

bundle_label = @Translation("Content type"), 

We can deduce that Node has bundles by the fact that it references the ID of the plugin defining the bundle configuration entity type:

bundle_entity_type = "node_type", 

Lo and behold, that is the NodeType's ConfigEntityType plugin ID. On its plugin annotation, we can find the reverse bundle_of property that references the Node entity type. Needless to say, this is not mandatory for all configuration entity types but used for the ones that act as content entity bundles. For example, the View configuration entity type does not have this.

In addition, we also find on the Node plugin ...