/**
  * {@inheritdoc}
  */
 public function getAllSources()
 {
     $targets = [];
     if ($this->isValid()) {
         $attributes = $this->attributeManager->getAttributes();
         foreach ($attributes as $attribute) {
             $targets[] = ['id' => $attribute->getCode(), 'text' => $attribute->getCode()];
         }
     }
     return $targets;
 }