private function resolveRootValue(ServerConfig $config, OperationParams $params, DocumentNode $doc, $operationType)
    {
        $root = $config->getRootValue();

        if (is_callable($root)) {
            $root = $root($params, $doc, $operationType);
        }

        return $root;
    }
private function resolveRootValue(ServerConfig $config, OperationParams $params, DocumentNode $doc, $operationType)
    {
        $root = $config->getRootValue();

        if (is_callable($root)) {
            $root = $root($params, $doc, $operationType);
        }

        return $root;
    }
@param string $operationType

@return mixed