code: function (params) {
      this.formatString = '';
      this.params = [];
  
      if (!params) {
        return;
      }
  
      params = utils.isArray(params) ? params : [params];
      if ((params.length > 0) &&
          utils.isString(params[0]) &&
          (params[0].indexOf('{}') !== -1)) {
        this.formatString = params[0];
        this.params = params.slice(1);
      }
      else {
        this.params = params;
      }
    }
docs: Definition of the Message class.
  
  If the first parameter in the message is a string that contains "{}", it
  is taken to be a format string, and the getFormattedMessage function will
  substitute the occurrences of "{}" with the serialization of the other
  parameters in order.
  
  @constructor
  @param {(string|Object|Array.<(string|Object)>)} params The parameters
  that compose the message.