private static String ind(int levels) {
        int indent = levels*STD_INDENT;
        StringBuilder sb = new StringBuilder();
        for (int i = 0 ; i<indent ; i++) {
            sb.append(" ");
        }
        return sb.toString();
    }
Returns spaces corresponding to the given levels of indentations
vespa-documentgen-plugin/src/main/java/com/yahoo/vespa/DocumentGenMojo.java