@Override
    public void endDocument() throws SAXException {
        super.endDocument();
        List<StandardReference> standards =
                StandardsText.extractStandardReferences(stringBuilder.toString(), threshold);
        for (StandardReference standardReference : standards) {
            metadata.add(STANDARD_REFERENCES, standardReference.toString());
        }
    }
This method is called whenever the Parser is done parsing the file. So,
we check the output for any standard references.
tika-core/src/main/java/org/apache/tika/sax/StandardsExtractingContentHandler.java