code: def add_tracks(self, subtracks):
          
          if isinstance(subtracks, Track):
              subtracks = [subtracks]
          for subtrack in subtracks:
              subtrack.subgroups['view'] = self.view
              self.add_child(subtrack)
              self.subtracks.append(subtrack)
docs: Add one or more tracks to this view.
  
          subtracks : Track or iterable of Tracks
              A single Track instance or an iterable of them.