code: public static function getTheme()
  	{
  		$theme = Config::get('backendTheme');
  		$rootDir = System::getContainer()->getParameter('kernel.project_dir');
  
  		if ($theme != '' && $theme != 'flexible' && is_dir($rootDir . '/system/themes/' . $theme))
  		{
  			return $theme;
  		}
  
  		return 'flexible';
  	}
docs: Return the current theme as string
  
  @return string The name of the theme