code: def _plumb_port(self, server, network_id, wrong_ips):
          
  
          for attached_interface in server.interface_list():
              if attached_interface.net_id == network_id:
                  if any(map(lambda x: x['ip_address'] in wrong_ips, attached_interface.fixed_ips)):
                      continue
                  return attached_interface
  
          return server.interface_attach(None, network_id, None)
docs: Look for an existing port on the network
          Add one if it doesn't exist