def METHOD_NAME(self):
    # T nodes are not customers of anyone
    for i in self.T:
        assert len(self.providers[i]) == 0
    # C nodes are not providers of anyone
    for i in self.C:
        assert len(self.customers[i]) == 0
    # CP nodes are not providers of anyone
    for i in self.CP:
        assert len(self.customers[i]) == 0
    # test whether there is a customer-provider loop
    for i in self.G.nodes():
        assert len(self.customers[i].intersection(self.providers[i])) == 0
    # test whether there is a peering with a customer or provider
    for i, j in self.G.edges():
        if self.G.edges[(i, j)]["type"] == "peer":
            assert j not in self.customers[i]
            assert i not in self.customers[j]
            assert j not in self.providers[i]
            assert i not in self.providers[j]