Device Handler Settings: How to use typeSettings?

When I create a new device handler, there is a Device Handler Settings section.
I want to enter name and value in this section and use it in the device handler code.
According to the guide, I can use typeSettings. . However, in actual use, it is NULL value.
A similar feature exists when creating a smartApp. In this case, use appSettings. .
Using appSettings. will not cause any problems.
I would like to use typeSettings. in the device handler, but how do I fix the problem?