def clean(self):
    cleaned_data = super().clean()
    if (cleaned_data.get('marked_flag') == Rating.FLAG_NONE):
        cleaned_data['comment'] = ''
    return cleaned_data
def clean(self):
    cleaned_data = super().clean()
    if (cleaned_data.get('marked_flag') == Rating.FLAG_NONE):
        cleaned_data['comment'] = 
    return cleaned_data