text: Title: Verify notebook-based pip install
  Body: I'm not familiar with the `collab` notebook environment.  I'm looking at all of our notebooks, and I see that we have text like `pip install hummingbird_ml[extra]` at the top of all of them. This was added by a `collab` user (ex: #150).
  
  I would expect this to be `pip install hummingbird-ml[extra]` with a dash, not underscore...but before I change it back maybe there is a notebook environment difference that I am not aware of!
  
  Could someone who is familiar with `collab` test our pip install import on both collab and jupyter in our notebook examples? And change it if necessary or close this issue if not?
  
  Thanks!!