public function get($id)
    {
        if (empty($this->instances[$id])) {
            $declarations = $this->getFeatureTypeDeclarations();
            if (empty($declarations[$id])) {
                throw new \RuntimeException("No FeatureType with id " . var_export($id, true));
            }
            $this->instances[$id] = new FeatureType($this->container, $declarations[$id]);
        }
        return $this->instances[$id];
    }