def get_xml(self):
        if not (self.respFat.valor or self.ferrEmi.valor):
            return ''
        xml = XMLNFe.get_xml(self)
        xml += u'<trafMut>'
        xml += self.respFat.xml            
        xml += self.ferrEmi.xml            
        xml += self.vFrete.xml            
        xml += self.chCTeFerroOrigem.xml
        for f in self.ferroEnv:
            xml += f.xml