creates an etree element of a ``SaltLabel`` that mimicks a SaltXMI
        <labels> element

def to_etree(self):
        """
        creates an etree element of a ``SaltLabel`` that mimicks a SaltXMI
        <labels> element
        """
        attribs = {
            '{{{pre}}}type'.format(pre=NAMESPACES['xsi']): self.xsi_type,
            'namespace': self.namespace, 'name': self.name,
            'value': self.hexvalue, 'valueString': self.value}
        non_empty_attribs = {key: val for (key, val) in attribs.items()
                             if val is not None}
        E = ElementMaker()
        return E('labels', non_empty_attribs)