yep - it's passed to `total_cost` function and it is list of ventures assigned to that service:
```
total_cost(self, start, end, service, forecast, ventures)
```
and check call of it in `costs` method:
```
service_cost = self.total_cost(
                dstart,
                dend,
                service,
                forecast,
                ventures=service.venture_set.all(),
            )
```
(https://github.com/kula1922/ralph_pricing/blob/feature/migrate-extra-costs/src/ralph_pricing/plugins/reports/service.py#L267)

As you can see, ventures variable contains exactly the same as your `ventures=Venture.objects.filter(service=service)` query