def METHOD_NAME(self):
    """Make a copy of the translation unit.
    We don't want to make a deep copy - this could duplicate the whole XML
    tree. For now we just serialise and reparse the unit's XML.
    """
    # TODO: check performance
    new_unit = self.__class__(None, empty=True)
    new_unit.xmlelement = etree.fromstring(etree.tostring(self.xmlelement))
    return new_unit