includeThemes example

/** * Scans all module, theme, and profile extensions and load the update files. * * @param string|null $extension * (optional) Limits the extension update files loaded to the provided * extension. */
  protected function scanExtensionsAndLoadUpdateFiles(string $extension = NULL) {
    // Scan for extensions.     $extension_discovery = new ExtensionDiscovery($this->root, TRUE, [], $this->sitePath);
    $module_extensions = $extension_discovery->scan('module');
    $theme_extensions = $this->includeThemes() ? $extension_discovery->scan('theme') : [];
    $profile_extensions = $extension_discovery->scan('profile');
    $extensions = array_merge($module_extensions, $theme_extensions, $profile_extensions);

    // Limit to a single extension.     if ($extension) {
      $extensions = array_intersect_key($extensions, [$extension => TRUE]);
    }

    $this->loadUpdateFiles($extensions);
  }