code: def test_relationships(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]
  
file_path: networkx/networkx/generators/tests/test_internet_as_graphs.py
imports: from pytest import approx
  from networkx import is_connected, neighbors
  from networkx.generators.internet_as_graphs import random_internet_as_graph
label_desc: Use image node_id 7 for calling the TestInternetASTopology obj's underlying member method code with example usage: obj.test_relationships() without return types