docs: @Nullable
    public IMicroDocument parseXHTMLFragment (@Nullable final String sXHTMLFragment)
    {
      // Build mini HTML and insert fragment in the middle.
      // If parsing succeeds, it is considered valid HTML.
      final String sHTMLNamespaceURI = m_eHTMLVersion.getNamespaceURI ();
      final String sXHTML = XMLEmitter.getDocTypeHTMLRepresentation (EXMLSerializeVersion.XML_10,
                                                                     EXMLIncorrectCharacterHandling.DEFAULT,
                                                                     m_eHTMLVersion.getDocType ()) +
                            "<html" +
                            (sHTMLNamespaceURI != null ? ' ' +
                                                         XMLConstants.XMLNS_ATTRIBUTE +
                                                         "=\"" +
                                                         sHTMLNamespaceURI +
                                                         '"'
                                                       : "") +
                            "><head><title></title></head><body>" +
                            StringHelper.getNotNull (sXHTMLFragment) +
                            "</body></html>";
      return parseXHTMLDocument (sXHTML);
    }