code: protected function getSearchFields(
          Criterion $criterion,
          $fieldDefinitionIdentifier,
          $fieldTypeIdentifier = null,
          $name = null
      ) {
          return $this->fieldNameResolver->getFieldTypes(
              $criterion,
              $fieldDefinitionIdentifier,
              $fieldTypeIdentifier,
              $name
          );
      }
docs: Get array of search fields.
  
  @param \eZ\Publish\API\Repository\Values\Content\Query\Criterion $criterion
  @param string $fieldDefinitionIdentifier
  @param string $fieldTypeIdentifier
  @param string $name
  
  @return array