title: ModuleNotFoundError: No module named 'threshold'
body: <p><a href="https://i.stack.imgur.com/84fX2.png" rel="nofollow noreferrer">code of the book</a>
  I am learing ML through the book <a href="https://github.com/luispedro/BuildingMachineLearningSystemsWithPython/blob/master/ch02/chapter.py" rel="nofollow noreferrer">Building MachineLearningSystemWithPython 2nd edition by Willi Richert and Luis Pedro Coelho</a>, and here in Chapter 2 it has used "fit_model" , and while looking for the code in GitHub of this book it has imported fit_model from threshold library as 
  "from threshold import fit_model" but it gives error while doing so. Sorry if this was a naive question.
  <a href="https://i.stack.imgur.com/84fX2.png" rel="nofollow noreferrer">error_while_trying</a></p>
  
  <p>I am trying this code in jupyter via anaconda-navigator and i have no idea what's worng.</p>