code: def from_etree(cls, etree_element):
          
          return cls(name=etree_element.attrib['name'],
                     value=etree_element.attrib['valueString'],
                     xsi_type=get_xsi_type(etree_element),
                     namespace=etree_element.attrib.get('namespace'),
                     hexvalue=etree_element.attrib['value'])
docs: creates a ``SaltLabel`` from an etree element representing a label
          element in a SaltXMI file.
  
          A label element in SaltXMI looks like this::
  
              <labels xsi:type="saltCore:SFeature" namespace="salt"
                  name="SNAME" value="ACED0005740007735370616E3139"
                  valueString="sSpan19"/>
  
          Parameters
          ----------
          etree_element : lxml.etree._Element
              an etree element parsed from a SaltXMI document