class YamlDiscoveryDecorator

class YamlDiscoveryDecorator extends YamlDiscovery {
    
    /**
     * The Discovery object being decorated.
     *
     * @var \Drupal\Component\Plugin\Discovery\DiscoveryInterface
     */
    protected $decorated;
    
    /**
     * Constructs a YamlDiscoveryDecorator object.
     *
     * @param \Drupal\Component\Plugin\Discovery\DiscoveryInterface $decorated
     *   The discovery object that is being decorated.
     * @param string $name
     *   The file name suffix to use for discovery; for instance, 'test' will
     *   become 'MODULE.test.yml'.
     * @param array $directories
     *   An array of directories to scan.
     */
    public function __construct(DiscoveryInterface $decorated, $name, array $directories) {
        parent::__construct($name, $directories);
        $this->decorated = $decorated;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getDefinitions() {
        return parent::getDefinitions() + $this->decorated
            ->getDefinitions();
    }
    
    /**
     * Passes through all unknown calls onto the decorated object.
     */
    public function __call($method, $args) {
        return call_user_func_array([
            $this->decorated,
            $method,
        ], $args);
    }

}