'Schedule a call to send_state_to_connections.
This function adds a delay in the hopes that additional updates will be
scheduled and they can all be called at once in a batch.
:param connections: An iterable of connections that will be passed to
``_send_state_to_connections``.'

def _schedule_update(self, connections):

    self._connections_pending_update.update(set(connections))
    if ((self._current_pending_update_delayed_call is None) and self._connections_pending_update):
        self._current_pending_update_delayed_call = self._reactor.callLater(CONTROL_SERVICE_BATCHING_DELAY, self._execute_update_connections)
