human
Solve the following python programming problem given the following code:
def contribute_to_class(self, cls, name) : 
    def register_source_group(source) : 
        setattr (cls, name, ImageSpecFileDescriptor (self, name, source)) 
        self._set_spec_id (cls, name) 
        register.source_group (self.spec_id, ImageFieldSourceGroup (cls, source)) 
if self.source : 
        register_source_group (cls.source) 
else : 
        def handle_model_preparation(sender, **kwargs) : 
            image_fields = [f.attname for f in cls._meta.fields if isinstance (f, models.ImageField)] 
            if (len (image_fields) == 0) : 
                raise Exception (('%s does not define any ImageFields, so your %s ImageSpecField has no image to act on.' % (cls.__name__, name))) 
else : 
                if (len (image_fields) > 1) : 
                    raise Exception (('%s defines multiple ImageFields, but you have not specified a source for your %s ImageSpecField.' % (cls.__name__, name))) 
register_source_group (image_fields [0]) 
class_prepared.connect (handle_model_preparation, sender = cls, weak = False) 

    
    

    Fix the buggy line: register_source_group (cls.source)
assistant
#Here is Python program to fix the buggy line: register_source_group (cls.

register_source_group (self.source)