function Dataflow() {
    this.logger(logger());
    this.logLevel(Error$1);
    this._clock = 0;
    this._rank = 0;
    this._locale = defaultLocale();
    try {
      this._loader = loader();
    } catch (e) {
      // do nothing if loader module is unavailable
    }
    this._touched = UniqueList(id);
    this._input = {};
    this._pulse = null;
    this._heap = Heap((a, b) => a.qrank - b.qrank);
    this._postrun = [];
  }
A dataflow graph for reactive processing of data streams.
@constructor