docs: def walk(self):
          """Return view on configured steps slice.
  
          Other Parameters:
              conf.core.snapshots: the slice of snapshots.
              conf.core.timesteps: the slice of timesteps.
          """
          if conf.core.snapshots is not None:
              return self.snaps[conf.core.snapshots]
          elif conf.core.timesteps is not None:
              return self.steps[conf.core.timesteps]
          return self.snaps[-1:]