private function preparePayload(array $payload)
    {
        return array_map(function ($payload) {
            if (!($payload instanceof TransferObjectInterface)) {
                return $payload;
            }

            return $payload->getIdentifier();
        }, $payload);
    }
private function preparePayload(array $payload)
    {
        return array_map(function ($payload) {
            if (!($payload instanceof TransferObjectInterface)) {
                return $payload;
            }

            return $payload->getIdentifier();
        }, $payload);
    }
@param array $payload

@return array