def serialize_to_transport(self, encoding='utf-8', xslt_url=None):
        """Serialize to XML ``bytes`` with prolog.

        Args:
          encoding: str
            Encoding to use for XML doc bytes
          xslt_url: str
            If specified, add a processing instruction to the XML doc that specifies the
            download location for an XSLT stylesheet.

        Returns:
          bytes: XML holding a DataONEError based type.

        """
        assert encoding in ('utf-8', 'UTF-8')
        dataone_exception_pyxb = self.get_pyxb()
        return d1_common.xml.serialize_for_transport(
            dataone_exception_pyxb, xslt_url=xslt_url
        )