private String getXHTMLHeaderTagName(Attributes atts) {
        String depthStr = atts.getValue(TEXT_NS, "outline-level");
        if (depthStr == null) {
            return "h1";
        }

        int depth = Integer.parseInt(depthStr);
        if (depth >= 6) {
            return "h6";
        } else if (depth <= 1) {
            return "h1";
        } else {
            return "h" + depth;
        }
    }
Mappings between ODF tag names and XHTML tag names
(including attributes). All other tag names/attributes are ignored
and left out from event stream.
tika-parsers/tika-parsers-standard/tika-parsers-standard-modules/tika-parser-miscoffice-module/src/main/java/org/apache/tika/parser/odf/OpenDocumentBodyHandler.java