def pdfa_status(self):
        """Returns the PDF/A conformance level claimed by this PDF, or False

        A PDF may claim to PDF/A compliant without this being true. Use an
        independent verifier such as veraPDF to test if a PDF is truly
        conformant.

        Returns:
            str: The conformance level of the PDF/A, or an empty string if the
            PDF does not claim PDF/A conformance. Possible valid values
            are: 1A, 1B, 2A, 2B, 2U, 3A, 3B, 3U.
        """
        key_part = QName(XMP_NS_PDFA_ID, 'part')
        key_conformance = QName(XMP_NS_PDFA_ID, 'conformance')
        try:
            return self[key_part] + self[key_conformance]
        except KeyError:
            return ''