def METHOD_NAME(self):
    G = nx.DiGraph()
    G.add_node(0)
    def kernel(x):
        return x
    assert nx.is_isomorphic(gn_graph(1), G)
    assert nx.is_isomorphic(gn_graph(1, kernel=kernel), G)
    assert nx.is_isomorphic(gnc_graph(1), G)
    assert nx.is_isomorphic(gnr_graph(1, 0.5), G)