public static function load($source, string $contentType = 'text/xml', array $options = []): \FluentDOM\DOM\Document {
    if (NULL === self::$_loader) {
      self::$_loader = self::getDefaultLoaders();
    }
    $result = self::$_loader->load($source, $contentType, $options);
    return $result instanceof \DOMDocument ? $result : $result->getDocument();
  }