public function getDependencies()
    {
        if (empty($this->dependencies)) {
            foreach ($this->getManifest()->getDependencies() as $id => $version) {
                $this->dependencies[$id] = $version;
                $dependence = $this->getExtensionManager()->getExtensionById($id);
                $this->dependencies = array_merge($this->dependencies, $dependence->getDependencies());
            }
        }
        return $this->dependencies;
    }