public function embedsOne($parent, string $relatedClass, string $relation = null): EmbedsOne
    {
        if (is_null($relation)) {
            list(, $caller) = debug_backtrace(false);
            $relation = $caller['function'];
        }

        $this->addEmbeddedRelation($relation);
        $this->addNonProxyRelation($relation);

        return new EmbedsOne($parent, $relatedClass, $relation);
    }