Neos\Flow\Package\PackageManagerInterface::getActivePackages PHP Method

    public function getActivePackages();

 public function initializeObject($reason)
 {
     if ($reason === ObjectManagerInterface::INITIALIZATIONCAUSE_RECREATED) {
         return;
     }
     /** @var Package $package */
     foreach ($this->packageManager->getActivePackages() as $package) {
         foreach ($package->getNamespaces() as $namespace) {
             $this->addNamespace(strtolower($package->getPackageKey()), $namespace . '\\ViewHelpers');
         }
     }
 }