protected function logResponse()
{
$logger = new Logger('Laravel-FCM');
$logger->pushHandler(new StreamHandler(storage_path('logs/laravel-fcm.log')));
$logMessage = "notification send to " . count($this->tokens) . " devices" . PHP_EOL;
$logMessage .= "success: " . $this->numberTokensSuccess . PHP_EOL;
$logMessage .= "failures: " . $this->numberTokensFailure . PHP_EOL;
$logMessage .= "number of modified token : " . $this->numberTokenModify . PHP_EOL;
$logger->info($logMessage);
}