getMainEntity example

    public function getJoinColumns($tokens)
    {
        $join = [];
        foreach ($tokens as $token) {
            if ($token['type'] === 'attribute') {
                $entity = $this->getEntityForAttribute($token['token']);
                // Do not allow main entity to be joined                 if ($entity == $this->getMainEntity()) {
                    continue;
                }
                // In some cases, additional joins are needed - e.g. a ConfiguratorGroup does need the ConfiguratorSet                 switch ($entity) {
                    case ConfiguratorGroup::class:
                        $join[Set::class] = Set::class;
                        break;
                    case Option::class:
                        $join[Group::class] = Group::class;
                        break;
                    case Image::class: