code: def transform(self, trajs_tuple, y=None):
          
          return [self.partial_transform(traj_zip)
                  for traj_zip in zip(*trajs_tuple)]
docs: Featurize a several trajectories.
  
          Parameters
          ----------
          traj_list : list(mdtraj.Trajectory)
              Trajectories to be featurized.
  
          Returns
          -------
          features : list(np.ndarray), length = len(traj_list)
              The featurized trajectories.  features[i] is the featurized
              version of traj_list[i] and has shape
              (n_samples_i, n_features)