code: function Flow(limit) {
    this.limit = limit;
    Object.defineProperty(this, "futureStack_", {
      enumerable: false,
      writable: true,
      value: []
    });
    Object.defineProperty(this, "runningNum_", {
      enumerable: false,
      writable: true,
      value: 0
    });
  }
docs: Flow class.