How to shrink pending wires to perform a shoulder on a face?

Here is the target result:

obtained with:
```
import cadquery as cq
result = cq.Workplane("front").box(2.0, 2.0, 0.5)
result = result.faces(">Y").workplane().rect(1.8,0.3).extrude(0.2)
show_object(result)
```
Instead, I would like to do it with something like this:
```
import cadquery as cq
result = cq.Workplane("front").box(2.0, 2.0, 0.5)
result = result.faces(">Y").wires().toPending().shrink(0.1).extrude(0.2)
show_object(result)
```

How can I do it please?