public XMLWriter openTag(Utf8String tag) {
        closeStartTag();
        if (openTags.size()>0) {
            w(LF);
            if (isFirstInParent && openTags.size()<=maxLineSeparatorLevel) {
                w(LF);
            }
            indent();
        }
        w(LT).w(tag);
        openTags.add(tag);
        inOpenStartTag=true;
        currentIsMultiline=false;
        isFirstInParent=true;
        return this;
    }
Writes the first line of an XML file
vespajlib/src/main/java/com/yahoo/text/XMLWriter.java