code: def _notify_single_item(self, item):
          
          # channels that this individual item has already triggered
          # (dont want to trigger them again)
          triggered_channels = set()
          for key_set in self.watch_keys:
              # only pluck keys if they exist
              plucked = {
                  key_name: item[key_name]
                  for key_name in key_set if key_name in item
              }
              route_keys = expand_dict_as_keys(plucked)
              for route in route_keys:
                  channels = self.get_route_items(route) or {}
                  LOG.debug('route table match: %s -> %s', route, channels)
                  if not channels:
                      LOG.debug(
                          'no subscribers for message.\nkey %s\nroutes: %s',
                          route,
                          self._routes
                      )
                  for channel in channels:
                      if channel in triggered_channels:
                          LOG.debug('skipping dispatch to %s', channel)
                          continue
                      LOG.debug('routing dispatch to %s: %s', channel, item)
                      try:
                          channel.notify(item) and triggered_channels.add(channel)
                      except Exception:  # noqa
                          LOG.exception('Channel notification failed')
          return triggered_channels
docs: Route inbound items to individual channels