docs: function(
      firstPattern, secondPattern, dateTimeSymbols, useFirstDateOnFirstPattern) {
    /**
     * Formatter_ to format the first part of the date interval.
     * @private {!DateTimeFormat}
     */
    this.firstPartFormatter_ = new DateTimeFormat(firstPattern, dateTimeSymbols);
  
    /**
     * Formatter_ to format the second part of the date interval.
     * @private {!DateTimeFormat}
     */
    this.secondPartFormatter_ =
        new DateTimeFormat(secondPattern, dateTimeSymbols);
  
    /**
     * Specifies if the first or the second date should be formatted by the
     * formatter of the first or second part of the date interval.
     * @private {boolean}
     */
    this.useFirstDateOnFirstPattern_ = useFirstDateOnFirstPattern;
  }