/**
  * Removes all loggers of this type (or descendant).
  * @param string $class_name
  */
 public function remove_loggers_of_type($class_name)
 {
     if (isset($this->logger)) {
         if (is_a($this->logger, $class_name)) {
             if (isset($this->logger->logger)) {
                 $this->logger = $this->logger->logger;
             } else {
                 $this->logger = null;
             }
         }
         if (isset($this->logger)) {
             $this->logger->remove_loggers_of_type($class_name);
         }
     }
 }