human
Solve the following python programming problem given the following code:
def _str_internal(self) : 
    'Internal helper function for both __str__ and __repr__.' 
    def get_name(thing) : 
        try : 
            return thing.__name__ 
except AttributeError : 
            return thing.__class__.__name__ 
combine_fn_str = get_name (self.combine_fn) 
    input_arg = (('(%s)' % get_name (self.input_type)) if self.input_type else '') 
    if ((combine_fn_str == 'sum') and (not combine_fn_str)) : 
        combine_call = '' 
else : 
        combine_call = (' %s%s' % (combine_fn_str, input_arg)) 
return ('Aggregator %s%s' % (self.name, combine_call)) 

    
    

    Fix the buggy line: if ((combine_fn_str == 'sum') and (not combine_fn_str)) :
assistant
#Here is Python code to fix the buggy line: if ((combine_fn_str == 'sum') and (not combine_fn_str)) :
.

if ((combine_fn_str == 'sum') and (not input_arg)) :