Python traitlets 模块，TraitType() 实例源码

def can_document_member(cls, member, membername, isattr, parent):
        return isinstance(member, TraitType)

def _get_additional_traits(cls):
        try:
            default = cls._additional_traits[0]
        except TypeError:
            default = cls._additional_traits

        if isinstance(default, T.TraitType):
            return default
        elif default:
            return T.Any()
        else:
            return None