src/vs/base/common/async.ts/TaskSequentializer/hasPending
class TaskSequentializer:	hasPending(taskId?: number): this is ITaskSequentializerWithPendingTask {
		if (!this._pending) {
			return false;
		}

		if (typeof taskId === 'number') {
			return this._pending.taskId === taskId;
		}

		return !!this._pending;
	}