human
Solve the following python programming problem given the following code:
def get_arc() : 
    "
    Aggregate the location data into an easy json structure:

        (None, total,
         [continent, total, [country, total, [region, total, [city, total]]]])

    The expected format of `data` is:

        {continent: {country: {region: {city: total}}}}

    Each outer total is the sum of its childrens' inner totals.
    " 
    def unpack(dict_) : 
        'Unpack a (key, (v1, v2)) structure into (key, v1, v2).' 
        return revsort (((a.strip (), b, c) for (a, (b, c)) in dict_.iteritems ())) 
revsort = (lambda xs : sorted (xs, key = itemgetter (1), reverse = True)) 
    (continents, world_sum) = ({ 
        
}, 0) 
    for (continent, country_dict) in G ['arc'].iteritems () : 
        (countries, continent_sum) = ({ 
            
}, 0) 
        for (country, region_dict) in country_dict.iteritems () : 
            (regions, country_sum) = ({ 
                
}, 0) 
            for (region, cities) in region_dict.iteritems () : 
                total = sum (cities.itervalues ()) 
                if total : 
                    cs = [(k.strip (), v) for (k, v) in cities.iteritems ()] 
                    regions [region] = [total, revsort (cs)] 
                    country_sum += total 
if country_sum : 
                countries [country] = [country_sum, unpack (regions)] 
                continent_sum += country_sum 
if continent_sum : 
            continents [continent] = [continent_sum, unpack (countries)] 
            world_sum += continent_sum 
return (None, world_sum, unpack (countries)) 

    
    

    Fix the buggy line: return (None, world_sum, unpack (countries))
assistant
#Here is Python code to fix the buggy line: return (None, world_sum, unpack (countries))
.

return (None, world_sum, unpack (continents))