code: def learn_transportation_mode(track, clf):
      
      for segment in track.segments:
          tmodes = segment.transportation_modes
          points = segment.points
          features = []
          labels = []
  
          for tmode in tmodes:
              points_part = points[tmode['from']:tmode['to']]
              if len(points_part) > 0:
                  features.append(extract_features_2(points_part))
                  labels.append(tmode['label'])
  
          clf.learn(features, labels)
docs: Inserts transportation modes of a track into a classifier
  
      Args:
          track (:obj:`Track`)
          clf (:obj:`Classifier`)