You don't see any changes, because you just defined the function which returns the custom stop distances, but is not assigned to any gate:
parkings = {
GATE : {
},
}
Most of the times, people customize the name, and then add the Stop position, so the example in the manual assume this, but of course you are not required to rename, so you can skip the name parameter with an extra comma, and define just the stop:
parkings = {
GATE : {
None : ( , Gate ),
},
}
That, assuming your rule can be applied to all gates of the "GATE" group, so "None" has been used here. If you wanted to apply it to a single parking, it would be like this:
parkings = {
GATE : {
1: ( , Gate ),
},
}
In this example, your custom stop position would be applied to just GATE 1