/**
  * {@inheritdoc}
  */
 public function toString($format = '')
 {
     $pluginInfo = $this->pluginList->getNext($this->subjectType, 'toString');
     if (!$pluginInfo) {
         return parent::toString($format);
     } else {
         return $this->___callPlugins('toString', func_get_args(), $pluginInfo);
     }
 }