public static function parseRelationshipPaths(array $paths)
    {
        $tree = [];

        foreach ($paths as $path) {
            list($primary, $nested) = array_pad(explode('.', $path, 2), 2, null);

            if (! isset($tree[$primary])) {
                $tree[$primary] = [];
            }

            if ($nested) {
                $tree[$primary][] = $nested;
            }
        }

        return $tree;
    }