protected function _getFieldsFor(FieldListAwareInterface $object)
    {
        if (is_null($object->getFields())) {
            return false;
        }
        if (is_string($object->getFields())) {
            return $object->getFields();
        }
        $alias = (is_null($object->getAlias())) ?
            $object->getTable() : $object->getAlias();
        $fields = [];
        foreach ($object->getFields() as $field) {
            $fields[] = "{$alias}.{$field}";
        }

        return implode(', ', $fields);
    }