code: public static function getSessionHash($strCookie)
  	{
  		@trigger_error('Using System::getSessionHash() has been deprecated and will no longer work in Contao 5.0. Use Symfony authentication instead.', E_USER_DEPRECATED);
  
  		$session = static::getContainer()->get('session');
  
  		if (!$session->isStarted())
  		{
  			$session->start();
  		}
  
  		return sha1($session->getId().$strCookie);
  	}
docs: Return the session hash
  
  @param string $strCookie The cookie name
  
  @return string The session hash
  
  @deprecated Deprecated since Contao 4.5, to be removed in Contao 5.0.
  Use Symfony authentication instead.