You are correct. I apologize for the mistake in my previous response. The 'Series' object does not have an attribute called 'header'. Instead, we can use the 'name' attribute to access the column name of a Series object.
To print the header of account_opened from the banking DataFrame using the 'name' attribute, we can use the following code:
```python
print(banking['account_opened'].name)
```
This will give us the same result as before, which is the name of the column 'account_opened'.