QST:
Hi, 
I am new to pandas. I was facing issue with openpyxl in append mode

```
import pandas as pd

col = ['Expiry','pnl']
df = pd.DataFrame([], columns=col)
writer = pd.ExcelWriter('asd.xlsx', engine='openpyxl', mode='a')

df.to_excel(writer, "Sheet1")

writer.save()
writer.close()
```

It runs successfully but when I open excel file it says
**We found a problem with some content. Do you want us to try to recover?**
I have searched for solution in internet. But nothing was working. Could you please help me?

- [x] I have searched the [[pandas] tag](https://stackoverflow.com/questions/tagged/pandas) on StackOverflow for similar questions.

- [ ] I have asked my usage related question on [StackOverflow](https://stackoverflow.com).

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