human
Solve the following python programming problem given the following code:
def build_component_list(compdict, custom = None, convert = update_classpath) : 
    'Compose a component list from a { class: order } dictionary.' 
    def _check_components(complist) : 
        if (len ({ convert (c) for c in complist }) != len (complist)) : 
            raise ValueError ('Some paths in {!r} convert to the same object, please update your settings'.format (complist)) 
def _map_keys(compdict) : 
        if isinstance (compdict, BaseSettings) : 
            compbs = BaseSettings () 
            for (k, v) in six.iteritems (compdict) : 
                prio = compdict.getpriority (k) 
                if (compbs.getpriority (convert (k)) == prio) : 
                    raise ValueError ('Some paths in {!r} convert to the same object, please update your settings'.format (list (compdict.keys ()))) 
else : 
                    compbs.set (convert (k), v, priority = prio) 
return compbs 
else : 
            _check_components (compdict) 
            return { convert (k) : v for (k, v) in six.iteritems (compdict) } 
if isinstance (custom, (list, tuple)) : 
        _check_components (custom) 
        return type (custom) ((convert (c) for c in custom)) 
if (compdict is not None) : 
        compdict.update (custom) 
compdict = without_none_values (_map_keys (compdict)) 
    return [k for (k, v) in sorted (six.iteritems (compdict), key = itemgetter (1))] 

    
    

    Fix the buggy line: if (compdict is not None) :
assistant
#Here is Python program to fix the buggy line: if (compdict is not None) :
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if (custom is not None) :