private function assertServersLoaded()
 {
     if (null !== $this->servers) {
         return;
     }
     $serversData = $this->rootModuleFileManager->getExtraKey(self::SERVERS_KEY);
     if ($serversData) {
         $jsonValidator = new JsonValidator();
         $errors = $jsonValidator->validate($serversData, __DIR__ . '/../../res/schema/servers-schema-1.0.json');
         if (count($errors) > 0) {
             throw new ValidationFailedException(sprintf("The extra key \"%s\" is invalid:\n%s", self::SERVERS_KEY, implode("\n", $errors)));
         }
     }
     $this->servers = new ServerCollection();
     $this->serversData = (array) $serversData;
     foreach ($this->serversData as $serverName => $serverData) {
         $this->servers->add($this->dataToServer($serverName, $serverData));
     }
 }