Mixin not working if it is used inside the loopack API instead of the endpoint.

EDIT:
Is not working when you are using it from the loopback API instead from endpoint "get".

app.findOne(
"where": "...",
"include": { "relation": 'users'}
  "includeThrough": {
    "fields": "type"
  }
) 

Is possible to modify the code in order to be able to work within the loopback javascript api?