detach() {
      const argops = this._argops;
      let i, n, item, op;
      if (argops) {
        for (i = 0, n = argops.length; i < n; ++i) {
          item = argops[i];
          op = item.op;
          if (op._targets) {
            op._targets.remove(this);
          }
        }
      }

      // remove references to the source and pulse object,
      // if present, to prevent memory leaks of old data.
      this.pulse = null;
      this.source = null;
    }
Detach this operator from the dataflow.
Unregisters listeners on upstream dependencies.