code: def read_backup(self, p_todolist=None, p_timestamp=None):
          
          if not p_timestamp:
              change_hash = hash_todolist(p_todolist)
              index = self._get_index()
              self.timestamp = index[[change[1] for change in index].index(change_hash)][0]
          else:
              self.timestamp = p_timestamp
  
          d = self.backup_dict[self.timestamp]
  
          self.todolist = TodoList(d[0])
          self.archive = TodoList(d[1])
          self.label = d[2]
docs: Retrieves a backup for p_timestamp or p_todolist (if p_timestamp is not
          specified) from backup file and sets timestamp, todolist, archive and
          label attributes to appropriate data from it.