code: def from_etree(cls, etree_element):
          
          ins = SaltEdge.from_etree(etree_element)
          # TODO: this looks dangerous, ask Stackoverflow about it!
          # convert SaltEdge into DominanceRelation
          ins.__class__ = DominanceRelation.mro()[0]
          ins.features = get_annotations(etree_element)
          return ins
docs: create a ``DominanceRelation`` instance from an etree element
          representing an <edges> element with xsi:type
          'sDocumentStructure:SDominanceRelation'.