code: public function getContentMetaFieldBoostFactor(ContentType $contentType, $fieldName)
      {
          $typeIdentifier = $contentType->identifier;
  
          if (!isset($this->map[self::$keyMetaFields][$typeIdentifier])) {
              $typeIdentifier = self::$keyAny;
          }
  
          if (!isset($this->map[self::$keyMetaFields][$typeIdentifier][$fieldName])) {
              $fieldName = self::$keyAny;
          }
  
          if (isset($this->map[self::$keyMetaFields][$typeIdentifier][$fieldName])) {
              return $this->map[self::$keyMetaFields][$typeIdentifier][$fieldName];
          }
  
          return $this->defaultBoostFactor;
      }
docs: Get boost factor for a Content meta field by the given $fieldName.
  
  @param \eZ\Publish\SPI\Persistence\Content\Type $contentType
  @param string $fieldName
  
  @return float