static String toSecondsString(long milliseconds) {
        StringBuilder builder = new StringBuilder().append(milliseconds / 1000L).append('.');
        long decimals = milliseconds % 1000;
        if (decimals < 100) {
            builder.append('0');
            if (decimals < 10) {
                builder.append('0');
            }
        }
        return builder.append(decimals).toString();
    }
@return a string with number of seconds with 3 decimals
container-core/src/main/java/com/yahoo/container/logging/FormatUtil.java