old_contents: from socket import AF_INET
  
  from bndl.net.node import Node
  from bndl.net.tests import NetTest
  
  
  class TCPTest(NetTest):
      node_count = 4
  
      def create_nodes(self):
          return [
              Node(loop=self.loop, addresses=[seed], seeds=self.seeds)
              for seed in self.seeds
          ]
  
      def test_connectivity(self):
          for node in self.nodes:
              for peer in node.peers.values():
                  self.assertEqual(peer.conn.socket_family(), AF_INET)
  
new_contents: from socket import AF_INET, AF_INET6
  
  from bndl.net.node import Node
  from bndl.net.tests import NetTest
  
  
  class TCPTest(NetTest):
      node_count = 4
  
      def create_nodes(self):
          return [
              Node(loop=self.loop, addresses=[seed], seeds=self.seeds)
              for seed in self.seeds
          ]
  
      def test_connectivity(self):
          for node in self.nodes:
              for peer in node.peers.values():
                  self.assertIn(peer.conn.socket_family(), (AF_INET, AF_INET6))
  
subject: allow to default to ipv6