code: protected function getResponseFormat(array $config)
      {
          if (isset($config['responseFormat'])) {
              if (!is_string($config['responseFormat'])) {
                  throw new \DomainException(
                      'responseFormat must reference a string',
                      self::ERR_INVALID_RESPONSEFORMAT
                  );
              }
              return $config['responseFormat'];
          }
          return '[ %link% ] "%title%" by %author%'
              . '; Length %duration%'
              . '; Published %published%'
              . '; Views %views%'
              . '; Likes %likes%';
      }
docs: Extracts a pattern for formatting video data from configuration.
  
  @param array $config
  @return string
  @throws \DomainException if format setting is invalid