public function listPluginDataBySubdirectory() {
    $plugin_types_data = $this->listPluginData('AnnotatedClassDiscovery');
    $plugin_types_data_by_subdirectory = [];
    foreach ($plugin_types_data as $plugin_id => $plugin_definition) {
      if (!empty($plugin_definition['subdir'])) {
        $subdir = substr($plugin_definition['subdir'], strlen('Plugin/'));

        $plugin_types_data_by_subdirectory[$subdir] = $plugin_definition;
      }
    }
    return $plugin_types_data_by_subdirectory;
  }