code: private function getIndexFieldType(
          ContentType $contentType,
          FieldDefinition $fieldDefinition,
          FieldType $fieldType
      ) {
          if (!$fieldType instanceof FieldType\TextField) {
              return $fieldType;
          }
  
          $fieldType = clone $fieldType;
          $fieldType->boost = $this->boostFactorProvider->getContentFieldBoostFactor(
              $contentType,
              $fieldDefinition
          );
  
          return $fieldType;
      }
docs: Return index field type for the given arguments.
  
  @param \eZ\Publish\SPI\Persistence\Content\Type $contentType
  @param \eZ\Publish\SPI\Persistence\Content\Type\FieldDefinition $fieldDefinition
  @param \eZ\Publish\SPI\Search\FieldType $fieldType
  
  @return \eZ\Publish\SPI\Search\FieldType