*   id = "content_entity_example_contact",
 *   label = @Translation("Contact entity"),
 *   handlers = {
 *     "view_builder" = "DrupalCoreEntityEntityViewBuilder",
 *     "list_builder" = "Drupalcontent_entity_exampleEntityControllerContactListBuilder",
 *     "form" = {
 *       "default" = "Drupalcontent_entity_exampleFormContactForm",
 *       "delete" = "Drupalcontent_entity_exampleFormContactDeleteForm",
 *     },
 *     "access" = "Drupalcontent_entity_exampleContactAccessControlHandler",
 *   },
 *   list_cache_contexts = { "user" },
 *   base_table = "drupal.contact",
 *   admin_permission = "administer contact entity",
 *   entity_keys = {
 *     "id" = "id",
 *     "label" = "name",
 *     "uuid" = "uuid"
 *   },

.......
  class Contact extends ContentEntityBase implements ContactInterface {

  use EntityChangedTrait;
.......