code: public function checkJumpTo($varValue, Contao\DataContainer $dc)
  	{
  		if ($varValue == $dc->id)
  		{
  			throw new Exception($GLOBALS['TL_LANG']['ERR']['circularReference']);
  		}
  
  		return $varValue;
  	}
docs: Prevent circular references
  
  @param mixed                $varValue
  @param Contao\DataContainer $dc
  
  @return mixed
  
  @throws Exception