Drupal 8.0.0 beta 12. More info: https://www.drupal.org/node/2514176

core/modules/migrate/src/Plugin/SourceEntityInterface.php

@@ -0,0 +1,32 @@
+<?php
+/**
+ * @file
+ * Contains \Drupal\migrate\Plugin\SourceEntityInterface.
+ */
+
+namespace Drupal\migrate\Plugin;
+
+/**
+ * Interface for sources providing an entity.
+ */
+interface SourceEntityInterface {
+
+  /**
+   * Whether this migration has a bundle migration.
+   *
+   * @return bool
+   *   TRUE when the bundle_migration key is required.
+   */
+  public function bundleMigrationRequired();
+
+  /**
+   * The entity type id (user, node etc).
+   *
+   * This function is used when bundleMigrationRequired() is FALSE.
+   *
+   * @return string
+   *   The entity type id.
+   */
+  public function entityTypeId();
+
+}