public function getChildOfClass($class)
    {
        // Check for namespace alias
        if (strpos($class, ':') !== false) {
            list($namespaceAlias, $simpleClassName) = explode(':', $class);
            $class = $this->em->getConfiguration()->getEntityNamespace($namespaceAlias) . '\\' . $simpleClassName;
        }
        foreach ($this->getChildren() as $child) {
            if ($child->getPage() instanceof $class) {
                return $child;
            }
        }

        return null;
    }