Feeds integration: mapper

Hi I'm trying to add a target for Faqfield on drupal 8
I created this code but is not showing the field on mapping targets.
Could anyone help me, please?

/* code is inside this path: /src/Feeds/Target/Faqfield.php */
<?php

namespace Drupal\faqfield\Feeds\Target;

use Drupal\Core\Field\FieldDefinitionInterface;
use Drupal\feeds\FieldTargetDefinition;
use Drupal\feeds\Plugin\Type\Target\FieldTargetBase;
use Drupal\feeds\Feeds\Target\StringTarget;
/**
* Defines a faqfield field mapper.
*
* @FeedsTarget(
* id = "faqfield_feeds_target",
* field_types = {"question", "answer", "answer_format", "delta"}
* )
*/
class Faqfield extends StringTarget {

// protected static function prepareTarget(FieldDefinitionInterface $field_definition) {
// return FieldTargetDefinition::createFromFieldDefinition($field_definition)
// ->addProperty('question')
// ->addProperty('answer')
// ->addProperty('answer_format')
// ->addProperty('delta');
// }

protected static function prepareTarget(FieldDefinitionInterface $field_definition) {
return FieldTargetDefinition::createFromFieldDefinition($field_definition)
->addProperty('question')
->addProperty('answer');
}
// protected function prepareValue(array &$variables) {
// $variables['question'] = Markup::create(trim(strip_tags($variables['question'])));
// $variables['answer'] = check_markup($variables['answer'], $variables['answer_format']);
// }
}