How to Group By with multiple columns?

**Is your feature request related to a problem? Please describe.**
I want can use `GroupBy `with list input column for dataframe

**Describe the solution you'd like**
A clear and concise description of what you want to happen.

It could be good like this and allow return with new dataframe
```
var groupBy = df.GroupBy(new string[] { "Area", "Level" });
```
Or :
```
df.GroupBy("Level", "Building Name").Select("Source File", "Area", "Level", "Building Name");
```
This is python :
```
df_report_grouped = df_report.groupby(['Building Name', 'Level'])['Area'].sum().reset_index()
```
**Describe alternatives you've considered**
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