def METHOD_NAME(self, old_state_set):
    """
    Return the state of the new machine corresponding to the
    set of old machine states represented by |state_set|. A new
    state will be created if necessary. If any of the old states
    are accepting states, the new state will be an accepting state
    with the highest priority action from the old states.
    """
    key = self.make_key(old_state_set)
    new_state = self.old_to_new_dict.get(key, None)
    if not new_state:
        action = self.highest_priority_action(old_state_set)
        new_state = self.new_machine.new_state(action)
        self.old_to_new_dict[key] = new_state
        self.new_to_old_dict[id(new_state)] = old_state_set
        #for old_state in old_state_set.keys():
        #new_state.merge_actions(old_state)
    return new_state