code: def add_tracks(self, track):
          
          from trackhub import BaseTrack
          if isinstance(track, BaseTrack):
              self.add_child(track)
              self._tracks.append(track)
          else:
              for t in track:
                  self.add_child(t)
                  self._tracks.append(t)
docs: Add a track or iterable of tracks.
  
          Parameters
          ----------
  
          track : iterable or Track
              Iterable of :class:`Track` objects, or a single :class:`Track`
              object.