Here's my codes:

```
import pandas as pd
df = pd.DataFrame({'id': ['a', 'a', 'b', 'b', 'b'],
                   'v1': [1, 2, 3 ,4, 5],
                   'v2': [7, 6, 5, 4, 3],
                   'v3': [2, 4, 6, 8, 10]})

df.groupby('id').agg({'v1': ['count', 'sum'],
                      'v2': 'mean',
                      'v3': 'sum'})

```

My issue is that every time I run this code (in jupyter notebook), the resulted dataframe have different column orders. Is this a bug in pandas?

My next step is to rename the resulted dataframe, but with no reproducible order, it is kinda impossible to write a reusable code to do that. How could I work around it?

Btw, I am using python 3.5 and pandas 0.23.0.

Thanks!