creates a ``SaltNode`` instance from the etree representation of an
        <nodes> element from a SaltXMI file.

def from_etree(cls, etree_element):
        """
        creates a ``SaltNode`` instance from the etree representation of an
        <nodes> element from a SaltXMI file.
        """
        ins = SaltElement.from_etree(etree_element)
        # TODO: this looks dangerous, ask Stackoverflow about it!
        ins.__class__ = SaltNode.mro()[0]  # convert SaltElement into SaltNode
        ins.layers = get_layer_ids(etree_element)
        ins.features = get_annotations(etree_element)
        return ins