def from_etree(cls, etree_element):
        """
        creates a `SaltElement` from an `etree._Element` representing
        an element in a SaltXMI file.
        """
        label_elements = get_subelements(etree_element, 'labels')
        labels = [SaltLabel.from_etree(elem) for elem in label_elements]
        return cls(name=get_element_name(etree_element),
                   element_id=get_graph_element_id(etree_element),
                   xsi_type=get_xsi_type(etree_element),
                   labels=labels,
                   xml=etree_element)
creates a `SaltElement` from an `etree._Element` representing
        an element in a SaltXMI file.