human
Solve the following python programming problem given the following code:
def _TestQueryUsers(tester, user_cookie, request_dict) : 
    'Called by the ServiceTester in order to test query_users
  service API call.
  ' 
    validator = tester.validator 
    (user_id, device_id) = tester.GetIdsFromCookie (user_cookie) 
    def _MakeMetadataDict(friend_user, forward_friend, reverse_friend) : 
        user_dict = { 
            'user_id' : friend_user.user_id, 
} 
        labels = list (friend_user.labels.intersection ([User.REGISTERED, User.TERMINATED])) 
        if (reverse_friend is not None) : 
            util.SetIfNotNone (user_dict, 'name', friend_user.name) 
            util.SetIfNotNone (user_dict, 'given_name', friend_user.given_name) 
            util.SetIfNotNone (user_dict, 'family_name', friend_user.family_name) 
            util.SetIfNotNone (user_dict, 'email', friend_user.email) 
            util.SetIfNotNone (user_dict, 'picture', friend_user.picture) 
            util.SetIfNotNone (user_dict, 'merged_with', friend_user.merged_with) 
            labels.append ('friend') 
user_dict ['labels'] = labels 
        if (friend_user.user_id == user_id) : 
            user_dict ['private'] = { 
                'subscriptions' : [], 
                'user_identities' : [], 
} 
            if (friend_user.pwd_hash is None) : 
                user_dict ['private'] ['no_password'] = True 
db_key = DBKey (('us:%d' % user_id), AccountSettings.GROUP_NAME) 
            settings = validator.GetModelObject (AccountSettings, db_key, must_exist = False) 
            if (settings is not None) : 
                settings_dict = user_dict ['private'].setdefault ('account_settings', { 
                    
}) 
                util.SetIfNotNone (settings_dict, 'email_alerts', settings.email_alerts) 
                util.SetIfNotNone (settings_dict, 'sms_alerts', settings.sms_alerts) 
                util.SetIfNotEmpty (settings_dict, 'storage_options', list (settings.storage_options)) 
predicate = (lambda ident : (ident.user_id == user_id)) 
            for expected_ident in...

    
    

    Fix the buggy line: forward_friend = validator.GetModelObject (Friend, DBKey (user_id, forward_friend), must_exist = False)
assistant
#Here is Python program to fix the buggy line: forward_friend = validator.

forward_friend = validator.GetModelObject (Friend, DBKey (user_id, friend_id), must_exist = False)