How to use the nose2.util.ancestry function in nose2

def _makeGroupTest(self, mod, group, parent_layer=None, position=0):
        layer = self._makeLayer(group, parent_layer, position)
        case = self._makeTestCase(group, layer, parent_layer)
        log.debug(
            "Made test case %s with layer %s from %s", case, layer, group)
        mod[layer.__name__] = layer
        layer.__module__ = mod['__name__']
        name = case.__name__
        long_name = ' '.join(
            [n[0].description for n in util.ancestry(layer)] + [name])
        mod[long_name] = case
        if name not in mod:
            mod[name] = case
        case.__module__ = mod['__name__']
        for index, child in enumerate(group._children):
            self._makeGroupTest(mod, child, layer, index)

def reportStartTest(self, event):
        if self.session.verbosity < 2:
            return
        test = event.testEvent.test
        layer = getattr(test, 'layer', None)
        if not layer:
            return
        for ix, lys in enumerate(util.ancestry(layer)):
            for layer in lys:
                if layer not in self.layersReported:
                    desc = self.describeLayer(layer)
                    event.stream.writeln('%s%s' % (self.indent * ix, desc))
                    self.layersReported.add(layer)
        event.stream.write(self.indent * (ix + 1))

def _allLayers(self, test, method, reverse=False):
        done = set()
        all_lys = util.ancestry(self.layer)
        if reverse:
            all_lys = [reversed(lys) for lys in reversed(all_lys)]
        for lys in all_lys:
            for layer in lys:
                if layer in done:
                    continue
                self._inLayer(layer, test, method)
                done.add(layer)