private void addLine(String line) {
        addIndent();
        str.append(line);
        str.append('\n');
    }
Add a complete line of output. Appropriate indentation will be added before the given string and a newline will
be added after it.

@param line the line we want to add
vespajlib/src/main/java/com/yahoo/vespa/objects/ObjectDumper.java