Cannot search for usages in python flow config

I have a Python flow configuration code similar to the following:

file: some_flow.py
```
flow = {
   ('module_one', 'func_one'): {
       OK: ('module_one', 'func_two'),
       ERR: ('module_one', 'func_err'),
       ABORT: None,
   },
   ('module_one', 'func_two'): {
       OK: ('module_one', 'func_three'),
       ERR: None,
       ABORT: None,
   },
   ('module_one', 'func_err'): {
       OK: None,
       ERR: None,
       ABORT: None,
   },
   ('module_one', 'func_three'): {
       # ...  
   },
}
```
Now, I want to add an "from" or "to" inlay hint after each step. When clicked, it should jump to the step's key or to where the step is referenced.

I have already implemented inlay hints, but I haven't figured out how to find usages yet.

I have extended the following classes, but I still can't achieve it:
```
FindUsagesHandlerFactory
FindUsagesHandler
ScalarIndexExtension<String>
QueryExecutorBase
PsiReferenceContributor
TaskFlowReference
```
What should I do to?