protected function parseNamespaces(ClassMetadata $metadata, $config)
    {
        if (!isset($config['namespaces'])) {
            return;
        }

        if (!is_array($config)) {
            throw new \RuntimeException(sprintf('Invalid YAML configuration for "%s" : "namespaces" property need to be an array.', $metadata->name));
        }

        foreach ($config['namespaces'] as $prefix => $uri) {
            $metadata->addGraphNamespace(new NamespaceNode([
                'prefix' => $prefix,
                'uri'    => $uri,
            ]));
        }
    }