tensor_stack.pop_back();
    auto op_id_it = tensor_tape.find(tensor_id);
    if (op_id_it == tensor_tape.end()) {
      continue;
    }
    int64_t op_id = op_id_it->second;
    auto op_it = op_tape->find(op_id);
    auto result_op_it = result.op_tape.find(op_id);
    if (op_id == -1 || op_it == op_tape->end() ||
        result_op_it != result.op_tape.end()) {
      continue;
    }

                        </Array>
                    </mxGeometry>
                </mxCell>

                    <mxGeometry x="450" y="-50" width="820" height="970" as="geometry"/>
                </mxCell>

                </mxCell>

                        <Array as="points"/>
                    </mxGeometry>
                </mxCell>

                    <mxGeometry x="420" y="280" width="920" height="670" as="geometry"/>
                </mxCell>

                    <mxGeometry x="450" y="-50" width="820" height="970" as="geometry"/>
                </mxCell>

        //
        // Note that there is a race condition here which can result in missing
        // a cyclic edge: it's possible for two threads to simultaneous find
        // "safe" edges which together form a cycle. Preventing this race
        // condition efficiently without _introducing_ deadlock is probably
        // tricky. For now, just accept the race condition---missing a warning

    assertThrows(IllegalArgumentException.class, () -> multiset.add(KEY, COUNT_TO_ADD));
  }

  /**
   * Simulate some of the races that can happen on add. We can't easily simulate the race that
   * happens when an {@link AtomicInteger#compareAndSet} fails, but we can simulate the case where
   * the putIfAbsent returns a non-null value, and the case where the replace() of an observed zero
   * fails.
   */

    }

    taskFaker.runTasks()
    assertEvents(
      "take plan 0",
      "plan 0 TCP connecting...",
    )

    taskFaker.advanceUntil(250.ms)
    assertEvents(
      "take plan 1",
      "plan 1 TCP connecting...",
    )

    taskFaker.advanceUntil(500.ms)
    assertEvents(
      "take plan 2",
      "plan 0 cancel",
      "plan 1 cancel",
    )