在测试poco官方提供的tutorial的时候，总是出现错误

Remove any following parts if does not have details about

**Describe the bug**
在测试poco官方提供的tutorial的时候，总是出现错误，按照这个代码运行的时候，拖动星星的顺序是从左到右第一个，第三个，第五个，然后就运行不下去了，甚至在拖动第三个的时候也停止了，

```
paste traceback here
```

**To Reproduce**
Steps to reproduce the behaviour:
1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

**Expected behaviour**
A clear and concise description of what you expected to happen.

**Screenshots**
If applicable, add screenshots to help explain your problem.

**python version:** `python3.6.5`

**poco version:** `1.0.69`
> You can get poco version via `pip freeze` command.

**Smartphone (please complete the following information):**
- Device: [e.g. google pixel 2]
- OS: [e.g. Android 8.1]
- more information if have

**Additional context**
Add any other context about the problem here.