public function permissions()
    {
        $permissions = $this->morphToMany(
            Config::get('laratrust.models.permission'),
            'user',
            Config::get('laratrust.tables.permission_user'),
            Config::get('laratrust.foreign_keys.user'),
            Config::get('laratrust.foreign_keys.permission')
        );

        if (Config::get('laratrust.use_teams')) {
            $permissions->withPivot(Config::get('laratrust.foreign_keys.team'));
        }

        return $permissions;
    }