Allow the selection of multiple columns at once
**Is your feature request related to a problem? Please describe.**

Similar to pandas, it would be great if we could select multiple columns at once.


**Describe the solution you'd like**
```python
my_dataset = ...  # Has columns ['idx', 'sentence', 'label']
idx, label = my_dataset[['idx', 'label']]
```

**Describe alternatives you've considered**
we can do `[dataset[col] for col in ('idx', 'label')]`

**Additional context**
This is of course very minor.
