code: protected function isUnique($instance)
      {
          foreach ($this->getCollection() as $entry) {
              if ($entry->getAnnotatedName() === $instance->getAnnotatedName()) {
                  return false;
              }
          }
  
          return true;
      }
docs: checks if annotated name does not exist already
  
  @param mixed $instance the direct instance
  
  @return bool