def lookup_class(self, new_class):
    'Translate a new class name to the old class name.'
    if (new_class in self.classes_dict):
        (old_class, class_dict) = self.classes_dict[new_class]
        if (old_class is not None):
            return old_class
    return None
Translate a new class name to the old class name.
def lookup_class(self, new_class):
    
    if (new_class in self.classes_dict):
        (old_class, class_dict) = self.classes_dict[new_class]
        if (old_class is not None):
            return old_class
    return None