void close(Map m)

Source 

void close(Map m) {
  if (m['rid'] is int) {
    int rid = m['rid'];
    if (_responses.containsKey(rid)) {
      _responses[rid]._close();
      Response resp = _responses.remove(rid);
      if (_traceCallbacks != null) {
        traceResponseRemoved(resp);
      }
    }
  }
}