如何设置列注释

我想用小马设置列注释,但找不到 comment 参数,

我想要下面这样的评论栏

class User(db.Entity):
    __tablename__ = 'account_collection'
    uid = Required(str, max_len=50, comment='unique user id')
    name = Required(str, max_len=50, comment='username')

但它不会起作用 TypeError: Attribute User.uid has unknown option 'comment'