code: def from_etree(cls, etree_element):
          
          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)
docs: creates a `SaltElement` from an `etree._Element` representing
          an element in a SaltXMI file.