code: protected function getSortFieldName(
          SortClause $sortClause,
          $contentTypeIdentifier,
          $fieldDefinitionIdentifier
      ) {
          return $this->fieldNameResolver->getSortFieldName(
              $sortClause,
              $contentTypeIdentifier,
              $fieldDefinitionIdentifier
          );
      }
docs: Get sort field name.
  
  @param \eZ\Publish\API\Repository\Values\Content\Query\SortClause $sortClause
  @param string $contentTypeIdentifier
  @param string $fieldDefinitionIdentifier
  
  @return array