Method getInstance

/**
 * Returns the global Document object, only creating it
 * if it doesn't already exist.
 *
 * @param   string  $type        The document type to instantiate
 * @param   array   $attributes  Array of attributes
 *
 * @return  static  The document object.
 *
 * @since       1.7.0
 * @deprecated  5.0 Use the \Joomla\CMS\Document\FactoryInterface instead
 */
public static function getInstance($type = 'html', $attributes = array())
{
    $signature = serialize(array($type, $attributes));
    if (empty(self::$instances[$signature])) {
        self::$instances[$signature] = CmsFactory::getContainer()->get(FactoryInterface::class)->createDocument($type, $attributes);
    }
    return self::$instances[$signature];
}