def taxonomy(self, concept, depth=3, fringe=2):
        def traversable(node, edge):
            # Follow parent-child edges.
            return edge.node2 == node and edge.type == "is-a"
        if not isinstance(concept, Node):
            concept = self[concept]
        g = self.copy(nodes=concept.flatten(depth, traversable))
        g = g.fringe(depth=fringe)
        g = [self[n.id] for n in g if n != concept]
        return g
Test for trackers in zone.
dataset/ETHPy150Open clips/pattern/pattern/graph/commonsense.py/Commonsense.taxonomy--crossover with--dataset/ETHPy150Open home-assistant/home-assistant/tests/components/test_proximity.py/TestProximity.test_device_trackers_in_zone