docs: def restore_from_disk(self, clean_old_snapshot=False):
          """Restore the state of the BF using previous snapshots.
  
          :clean_old_snapshot: Delete the old snapshot on the disk (period < current - expiration)
          """
          base_filename = "%s/%s_%s_*.dat" % (self.snapshot_path, self.name, self.expiration)
          availables_snapshots = glob.glob(base_filename)
          last_period = self.current_period - dt.timedelta(days=self.expiration-1)
          for filename in availables_snapshots:
              snapshot_period = dt.datetime.strptime(filename.split('_')[-1].strip('.dat'), "%Y-%m-%d")
              if snapshot_period <  last_period and not clean_old_snapshot:
                  continue
              else:
                  self._union_bf_from_file(filename)
                  if snapshot_period == self.current_period:
                      self._union_bf_from_file(filename, current=True)
  
              if snapshot_period < last_period and clean_old_snapshot:
                  os.remove(filename)
          self.ready = True