code: function set(props, req, language) {
    if(language) {
      req.language = language;
    }
    else {
      language = req.language = acceptLanguage.get(req.headers['accept-language']);
    }
  
    if(typeof props.localizations === 'function') {
      req.localizations = props.localizations(language);
    }
  }
docs: Set locals and call localizations
  
  @param {Object} props requestLanguage.props
  @param {Object} req Express request
  @param {String} language
  @return void
  @private