human
Solve the following python programming problem given the following code:
def _get_progress(user, force_generation = False) : 
    def generate() : 
        achievements = Achievement.get_achievements_by_user_for_today (user) 
        def ea(achievement) : 
            try : 
                return Achievement.evaluate (user, achievement ['id']) 
except FormularEvaluationException as e : 
                return { 
                    'error' : ('Cannot evaluate formular: ' + e.message), 
                    'id' : achievement ['id'], 
} 
except Exception as e : 
                tb = traceback.format_exc () 
                return { 
                    'error' : tb, 
                    'id' : achievement ['id'], 
} 
check = (lambda x : ((x != None) and (not x.has_key ('error')) and ((x ['hidden'] == False) or (x ['level'] > 0)))) 
        evaluatelist = [ea (achievement) for achievement in achievements] 
        ret = { 
            'achievements' : { x ['id'] : x for x in evaluatelist if check (x) }, 
            'achievement_errors' : { x ['id'] : x for x in evaluatelist if ((x != None) and x.has_key ('error')) }, 
} 
        return (render ('json', ret), ret) 
key = ('/progress/' + str (user.id)) 
    if (not force_generation) : 
        return (get_or_set (key, (lambda : generate () [0])), None) 
else : 
        (ret_str, ret) = generate () 
        set_value (key, ret_str) 
        return (ret_str, key) 

    
    

    Fix the buggy line: return (ret_str, key)
assistant
#Here is Python program to fix the buggy line: return (ret_str, key)
.

return (ret_str, ret)