docs: def filter_unbound_ports(query):
      """Filter ports not bound to a host or network"""
      # hack for pep8 E711: comparison to None should be
      # 'if cond is not None'
      none = None
      port_model = models_v2.Port
      binding_level_model = ml2_models.PortBindingLevel
      query = (query
               .join_if_necessary(port_model)
               .join_if_necessary(binding_level_model)
               .filter(
                   binding_level_model.host != '',
                   port_model.device_id != none,
                   port_model.network_id != none))
      return query