Thank you, Steven.
> There is a feature-request to support that (as Python 2.7 does):
> but it is stalled.
I passed over the ticket.
Now, I know that this is a bug, but has not fixed yet.
There are (or ware ?) problems about performance and integrity for handling
It seems that a narrow range of use-cases cause the stalling.
Someday we have a type-focused VERY NICE library, (I hope that) it will be