def get_xml(self):
        if not (self.nONU.valor or self.qTotEmb.valor or self.infTotAP is not None):
            return ''
        xml = XMLNFe.get_xml(self)
        xml += u'<peri>'
        xml += self.nONU.xml
        xml += self.qTotEmb.xml
        xml += self.infTotAP.xml
        xml += '</peri>'
        return xml